Bio-inspired design of dental multilayers: experiments and model.
Niu, Xinrui; Rahbar, Nima; Farias, Stephen; Soboyejo, Wole
2009-12-01
This paper combines experiments, simulations and analytical modeling that are inspired by the stress reductions associated with the functionally graded structures of the dentin-enamel-junctions (DEJs) in natural teeth. Unlike conventional crown structures in which ceramic crowns are bonded to the bottom layer with an adhesive layer, real teeth do not have a distinct "adhesive layer" between the enamel and the dentin layers. Instead, there is a graded transition from enamel to dentin within a approximately 10 to 100 microm thick regime that is called the Dentin Enamel Junction (DEJ). In this paper, a micro-scale, bio-inspired functionally graded structure is used to bond the top ceramic layer (zirconia) to a dentin-like ceramic-filled polymer substrate. The bio-inspired functionally graded material (FGM) is shown to exhibit higher critical loads over a wide range of loading rates. The measured critical loads are predicted using a rate dependent slow crack growth (RDEASCG) model. The implications of the results are then discussed for the design of bio-inspired dental multilayers. PMID:19716103
Substrate Creep on The Fatigue Life of A Model Dental Multilayer Structure
Zhou, J; Huang, M; Niu, X; soboyejo, W
2006-10-09
In this paper, we investigated the effects of substrate creep on the fatigue behavior of a model dental multilayer structure, in which a top glass layer was bonded to a polycarbonate substrate through a dental adhesive. The top glass layers were ground using 120 grit or 600 grit sand papers before bonding to create different sub-surface crack sizes and morphologies. The multilayer structures were tested under cyclic Hertzian contact loading to study crack growth and obtain fatigue life curves. The experiment results showed that the fatigue lives of the multilayer structures were impaired by increasing crack sizes in the sub-surfaces. They were also significantly reduced by the substrate creep when tested at relatively low load levels i.e. P{sub m} < 60 N (Pm is the maximum magnitude of cyclic load). But at relatively high load levels i.e. P{sub m} > 65 N, slow crack growth (SCG) was the major failure mechanisms. A modeling study was then carried out to explore the possible failure mechanisms over a range of load levels. It is found that fatigue life at relatively low load levels can be better estimated by considering the substrate creep effect (SCE).
Creep-assisted slow crack growth in bio-inspired dental multilayers.
Du, Jing; Niu, Xinrui; Soboyejo, Wole
2015-06-01
Ceramic crown structures under occlusal contact are often idealized as flat multilayered structures that are deformed under Hertzian contact loading. Previous models treated each layer as linear elastic materials and resulted in differences between the measured and predicted critical loads. This paper examines the combined effects of creep (in the adhesive and substrate layers) and creep-assisted slow crack growth (in the ceramic layer) on the contact-induced deformation of bio-inspired, functionally graded multilayer (FGM) structures and the conventional tri-layers. The time-dependent moduli of each of the layers were determined from constant load creep tests. The resulting modulus-time characteristics were modeled using Prony series. These were then incorporated into a finite element model for the computation of stress distributions in the sub-surface regions of the top ceramic layer, in which sub-surface radial cracks, are observed as the clinical failure mode. The time-dependent stresses are incorporated into a slow crack growth (SCG) model that is used to predict the critical loads of the dental multilayers under Hertzian contact loading. The predicted loading rate dependence of the critical loads is shown to be consistent with experimental results. The implications of the results are then discussed for the design of robust dental multilayers. PMID:25771255
Multilayer weighted social network model
NASA Astrophysics Data System (ADS)
Murase, Yohsuke; Török, János; Jo, Hang-Hyun; Kaski, Kimmo; Kertész, János
2014-11-01
Recent empirical studies using large-scale data sets have validated the Granovetter hypothesis on the structure of the society in that there are strongly wired communities connected by weak ties. However, as interaction between individuals takes place in diverse contexts, these communities turn out to be overlapping. This implies that the society has a multilayered structure, where the layers represent the different contexts. To model this structure we begin with a single-layer weighted social network (WSN) model showing the Granovetterian structure. We find that when merging such WSN models, a sufficient amount of interlayer correlation is needed to maintain the relationship between topology and link weights, while these correlations destroy the enhancement in the community overlap due to multiple layers. To resolve this, we devise a geographic multilayer WSN model, where the indirect interlayer correlations due to the geographic constraints of individuals enhance the overlaps between the communities and, at the same time, the Granovetterian structure is preserved.
Dental cell sheet biomimetic tooth bud model.
Monteiro, Nelson; Smith, Elizabeth E; Angstadt, Shantel; Zhang, Weibo; Khademhosseini, Ali; Yelick, Pamela C
2016-11-01
Tissue engineering and regenerative medicine technologies offer promising therapies for both medicine and dentistry. Our long-term goal is to create functional biomimetic tooth buds for eventual tooth replacement in humans. Here, our objective was to create a biomimetic 3D tooth bud model consisting of dental epithelial (DE) - dental mesenchymal (DM) cell sheets (CSs) combined with biomimetic enamel organ and pulp organ layers created using GelMA hydrogels. Pig DE or DM cells seeded on temperature-responsive plates at various cell densities (0.02, 0.114 and 0.228 cells 10(6)/cm(2)) and cultured for 7, 14 and 21 days were used to generate DE and DM cell sheets, respectively. Dental CSs were combined with GelMA encapsulated DE and DM cell layers to form bioengineered 3D tooth buds. Biomimetic 3D tooth bud constructs were cultured in vitro, or implanted in vivo for 3 weeks. Analyses were performed using micro-CT, H&E staining, polarized light (Pol) microscopy, immunofluorescent (IF) and immunohistochemical (IHC) analyses. H&E, IHC and IF analyses showed that in vitro cultured multilayered DE-DM CSs expressed appropriate tooth marker expression patterns including SHH, BMP2, RUNX2, tenascin and syndecan, which normally direct DE-DM interactions, DM cell condensation, and dental cell differentiation. In vivo implanted 3D tooth bud constructs exhibited mineralized tissue formation of specified size and shape, and SHH, BMP2 and RUNX2and dental cell differentiation marker expression. We propose our biomimetic 3D tooth buds as models to study optimized DE-DM cell interactions leading to functional biomimetic replacement tooth formation. PMID:27565550
A MULTILAYER BIOCHEMICAL DRY DEPOSITION MODEL 1. MODEL FORMULATION
A multilayer biochemical dry deposition model has been developed based on the NOAA Multilayer Model (MLM) to study gaseous exchanges between the soil, plants, and the atmosphere. Most of the parameterizations and submodels have been updated or replaced. The numerical integration ...
Multilayered models for electromagnetic reflection amplitudes
NASA Technical Reports Server (NTRS)
Linlor, W. I.
1976-01-01
The remote sensing of snowpack characteristics with surface installations or with an airborne system could have important applications in water resource management and flood prediction. To derive some insight into such applications, the electromagnetic response of multilayer snow models is analyzed. Normally incident plane waves are assumed at frequencies ranging from 10 to the 6th power to 10 to the 10th power Hz, and amplitude reflection coefficients are calculated for models having various snow-layer combinations, including ice sheets. Layers are defined by a thickness, permittivity, and conductivity; the electrical parameters are constant or prescribed functions of frequency. To illustrate the effect of various layering combinations, results are given in the form of curves of amplitude reflection coefficients, versus frequency for a variety of models. Under simplifying assumptions, the snow thickness and effective dielectric constant can be estimated from the reflection coefficient variations as a function of frequency.
A MULTILAYER BIOCHEMICAL DRY DEPOSITION MODEL 2. MODEL EVALUATION
The multilayer biochemical dry deposition model (MLBC) described in the accompanying paper was tested against half-hourly eddy correlation data from six field sites under a wide range of climate conditions with various plant types. Modeled CO_{2}, O_{3}, SO_{2<...}
Epidemic Model with Isolation in Multilayer Networks
NASA Astrophysics Data System (ADS)
Zuzek, L. G. Alvarez; Stanley, H. E.; Braunstein, L. A.
2015-07-01
The Susceptible-Infected-Recovered (SIR) model has successfully mimicked the propagation of such airborne diseases as influenza A (H1N1). Although the SIR model has recently been studied in a multilayer networks configuration, in almost all the research the isolation of infected individuals is disregarded. Hence we focus our study in an epidemic model in a two-layer network, and we use an isolation parameter w to measure the effect of quarantining infected individuals from both layers during an isolation period tw. We call this process the Susceptible-Infected-Isolated-Recovered (SIIR) model. Using the framework of link percolation we find that isolation increases the critical epidemic threshold of the disease because the time in which infection can spread is reduced. In this scenario we find that this threshold increases with w and tw. When the isolation period is maximum there is a critical threshold for w above which the disease never becomes an epidemic. We simulate the process and find an excellent agreement with the theoretical results.
Epidemic Model with Isolation in Multilayer Networks
Zuzek, L. G. Alvarez; Stanley, H. E.; Braunstein, L. A.
2015-01-01
The Susceptible-Infected-Recovered (SIR) model has successfully mimicked the propagation of such airborne diseases as influenza A (H1N1). Although the SIR model has recently been studied in a multilayer networks configuration, in almost all the research the isolation of infected individuals is disregarded. Hence we focus our study in an epidemic model in a two-layer network, and we use an isolation parameter w to measure the effect of quarantining infected individuals from both layers during an isolation period tw. We call this process the Susceptible-Infected-Isolated-Recovered (SIIR) model. Using the framework of link percolation we find that isolation increases the critical epidemic threshold of the disease because the time in which infection can spread is reduced. In this scenario we find that this threshold increases with w and tw. When the isolation period is maximum there is a critical threshold for w above which the disease never becomes an epidemic. We simulate the process and find an excellent agreement with the theoretical results. PMID:26173897
A refined model for characterizing x-ray multilayers
Oren, A.L.; Henke, B.L.
1987-12-01
The ability to quickly and accurately characterize arbitrary multilayers is very valuable for not only can we use the characterizations to predict the reflectivity of a multilayer for any soft x-ray wavelength, we also can generalize the results to apply to other multilayers of the same type. In addition, we can use the characterizations as a means of evaluating various sputtering environments and refining sputtering techniques to obtain better multilayers. In this report we have obtained improved characterizations for sample molybdenum-silicon and vanadium-silicon multilayers. However, we only examined five crystals overall, so the conclusions that we could draw about the structure of general multilayers is limited. Research involving many multilayers manufactured under the same sputtering conditions is clearly in order. In order to best understand multilayer structures it may be necessary to further refine our model, e.g., adopting a Gaussian form for the interface regions. With such improvements we can expect even better agreement with experimental values and continued concurrence with other characterization techniques. 18 refs., 30 figs., 7 tabs.
Characterization Of Multilayer X-Ray Analyzers: Models And Measurements
NASA Astrophysics Data System (ADS)
Henke, B. L.; Uejio, J. Y.; Yamada, H. T.; Tackaberry, R. E.
1986-08-01
A procedure is described for a detailed characterization of multilayer analyzers that can be effectively applied to their design, optimization, and application for absolute x-ray spectrometry in the 100 to 10,000 eV photon energy region. An accurate analytical model has been developed that is based upon a simple modification of the dynamical Darwin-Prins theory to extend its application to finite multilayer systems and to the low energy x-ray region. Its equivalence to the optical E&M solution of the Fresnel equations at each interface is demonstrated by detailed comparisons for the reflectivity of a multilayer throughout the angular range of incidence of 0° to 90°. A special spectrograph and an experimental method are described for the measurement of the absolute reflectivity characteristics of the multilayer. The experimental measurements at three photon energies in the 100 to 2000 eV region are fit by the analytical modified Darwin-Prins equation (MDP) for 1(0), generating a detailed characterization of two state-of-the-art multilayers: sputtered tungsten-carbon with 2d 70 A and a molecular lead stearate with 2d 100 A. The fitting parameters that are determined by this procedure are applied to help establish the structural characteristics of these multilayers.
Dental time study results in relation to a model for a dental health related patient group system.
Swedberg, Y
1995-01-01
Using a time study method, dental care treatment resources were studied concerning different caries groups of children and adolescents 3-19 years of age. The results were applied to a model for a dental health related patient group system as a tool for presenting the dental care situation. Quality assurance aspects of a dental health related patient group system, adapted for use in general dental care, had led to a suggested model system: "Dental Visiting Groups" (DVG). The DVG system takes into consideration the fact that dental care was performed by three dental care-giving personnel groups--dentists, dental hygienists and dental assistants--giving dental care in three main areas of dental procedures: diagnostic, prevention and intervention. The DVG system implied a model of Swedish dentistry in change, and presented the relationships among the dental health related patient groups, the three main areas of dental procedures, and the tasks of the dental care-givers. Applied over time, the DVG system illustrated the efficiency of the dental care model used. PMID:7676387
Modeling of thermal stresses in elastic multilayer coating systems
NASA Astrophysics Data System (ADS)
Gao, Chunxue; Zhao, Zhiwei; Li, Xuehua
2015-02-01
The performance and reliability of multilayer coating systems are strongly influenced by thermal stresses. The present study develops an alternative analytical model to predict the thermal stresses in elastic multilayer coating systems. An exact closed-form solution is obtained which is independent of the number of coating layers. In addition, with the definition of the coordinate system, the closed-form solution is concisely formulated. Specific results are calculated for thermal stresses in HfO2/SiO2 multilayer optical coatings, and a finite element analysis is performed to confirm the analytical results. The two results agree fairly well with each other. Also, when the thicknesses of the coating layers are much less than the substrate thickness, the approximate solution is obtained based on the exact closed-form solution, and its accuracy is examined.
Numerical FEM modeling in dental implantology
NASA Astrophysics Data System (ADS)
Roateşi, Iulia; Roateşi, Simona
2016-06-01
This paper is devoted to a numerical approach of the stress and displacement calculation of a system made up of dental implant, ceramic crown and surrounding bone. This is the simulation of a clinical situation involving both biological - the bone tissue, and non-biological - the implant and the crown, materials. On the other hand this problem deals with quite fine technical structure details - the threads, tapers, etc with a great impact in masticatory force transmission. Modeling the contact between the implant and the bone tissue is important to a proper bone-implant interface model and implant design. The authors proposed a three-dimensional numerical model to assess the biomechanical behaviour of this complex structure in order to evaluate its stability by determining the risk zones. A comparison between this numerical analysis and clinical cases is performed and a good agreement is obtained.
The Arizona model: a new paradigm for dental schools.
Smith, Kneka P; Woldt, Janet L; Cottam, Wayne W; Cederberg, Robert A
2011-01-01
The traditional method for the delivery of didactic instruction and patient care in dental schools has come under fire from a number of sources over the past several years. The American Dental Education Association and others have outlined numerous issues impeding the swift progression of student learning through the dental curriculum. Declining state revenues allotted to dental education, the increasing shortage of dental faculty, and the management of student learning in an already overcrowded dental school curriculum have led to the investigation of strategies that address solutions to these and other shortcomings in the current milieu of dental education. To address these deficiencies, strategies for change have been suggested. This article describes the development, implementation, and assessment of a new dental school that addresses these and other challenges to the education of today's dental student, thus creating the Arizona Model. Following seven years of operation, outcomes analysis at the Arizona School of Dentistry & Oral Health has shown positive trends in controlling educational costs, a shift to a modular curriculum, increasing student clinical experiences, and, consistent with the mission of the school, producing dentists who are well prepared for dental public health service. PMID:21205723
Numerical modeling of hydrofracturing in a multilayer coal seam
Nasedkina, A.A.; Trufanov, V.N.
2006-01-15
The mathematical model of the process for hydrodynamic fracturing in a multilayer coal seam is proposed. The model is based on the equation of continuity and Darcy's law. The filtration-temperature analogy allows solving the obtained non-linear, non-stationary problem in an axisymmetric statement for the pressure function as the heat-conductivity problem, by the finite-element method. The calculation results yield estimation of the radius of degassing borehole influence zone.
A Model Program for Dental Assisting Education in California.
ERIC Educational Resources Information Center
California State Dept. of Education, Sacramento. Bureau of Industrial Education.
Intended to provide assistance for developing new programs and improving existing ones, the guide was constructed by dental assisting instructors and other professional participants in a 196 5 workshop conference. Elements of the model program were derived from a statistical analysis of California junior colleg e programs in dental assisting and…
Dental Hygiene Curriculum Model for Transition to Future Roles.
ERIC Educational Resources Information Center
Paarmann, Carlene S.; And Others
1990-01-01
The establishment of the baccalaureate degree as the minimum entry level for dental hygiene practice centers around three main concerns: changes in health care delivery, awarding of a degree commensurate with students' educational background, and the credibility of dental hygiene as a profession. A curriculum model is discussed. (MLW)
Evaluation of the SEI using a multilayer spectroscopic ellipsometry model
Eric J. Dufek
2014-08-01
A multilayer spectroscopic ellipsometry (SE) model has been developed to characterize SEI formation. The model, which consists of two Cauchy layers, is constructed with an inner layer meant to model primarily inorganic compounds adjacent to an electrode and an outer layer which mirrors polymeric, organic constituents on the exterior of the SEI. Comparison of 1:1 EC:EMC and 1:4 EC:EMC with 1.0 M LiPF6 shows distinct differences in the two modeled layers. The data suggest that the thickness of both layers change over a wide potential range. These changes have been linked with other reports on the growth of the SEI.
Evaluation of the SEI using a multilayer spectroscopic ellipsometry model
Dufek, Eric J.
2014-08-28
A multilayer spectroscopic ellipsometry (SE) model has been developed to characterize SEI formation. The model, which consists of two Cauchy layers, is constructed with an inner layer meant to model primarily inorganic compounds adjacent to an electrode and an outer layer which mirrors polymeric, organic constituents on the exterior of the SEI. Comparison of 1:1 EC:EMC and 1:4 EC:EMC with 1.0 M LiPF₆ shows distinct differences in the two modeled layers. The data suggest that the thickness of both layers change over a wide potential range. These changes have been linked with other reports on the growth of the SEI.
Experimentally validated finite element model of electrocaloric multilayer ceramic structures
NASA Astrophysics Data System (ADS)
Smith, N. A. S.; Rokosz, M. K.; Correia, T. M.
2014-07-01
A novel finite element model to simulate the electrocaloric response of a multilayer ceramic capacitor (MLCC) under real environment and operational conditions has been developed. The two-dimensional transient conductive heat transfer model presented includes the electrocaloric effect as a source term, as well as accounting for radiative and convective effects. The model has been validated with experimental data obtained from the direct imaging of MLCC transient temperature variation under application of an electric field. The good agreement between simulated and experimental data, suggests that the novel experimental direct measurement methodology and the finite element model could be used to support the design of optimised electrocaloric units and operating conditions.
Experimentally validated finite element model of electrocaloric multilayer ceramic structures
Smith, N. A. S. E-mail: maciej.rokosz@npl.co.uk Correia, T. M. E-mail: maciej.rokosz@npl.co.uk; Rokosz, M. K. E-mail: maciej.rokosz@npl.co.uk
2014-07-28
A novel finite element model to simulate the electrocaloric response of a multilayer ceramic capacitor (MLCC) under real environment and operational conditions has been developed. The two-dimensional transient conductive heat transfer model presented includes the electrocaloric effect as a source term, as well as accounting for radiative and convective effects. The model has been validated with experimental data obtained from the direct imaging of MLCC transient temperature variation under application of an electric field. The good agreement between simulated and experimental data, suggests that the novel experimental direct measurement methodology and the finite element model could be used to support the design of optimised electrocaloric units and operating conditions.
ERIC Educational Resources Information Center
Dennison, Darwin
An investigation was conducted to determine the effects of instruction upon the dental health behavior of university students. The experimental group of 68 subjects, all elementary education majors, were exposed to a three--stage dental health motivational model: Dental Health Skills Instruction (four hours of laboratory instruction), Cognitive…
Interactive Tooth Separation from Dental Model Using Segmentation Field.
Li, Zhongyi; Wang, Hao
2016-01-01
Tooth segmentation on dental model is an essential step of computer-aided-design systems for orthodontic virtual treatment planning. However, fast and accurate identifying cutting boundary to separate teeth from dental model still remains a challenge, due to various geometrical shapes of teeth, complex tooth arrangements, different dental model qualities, and varying degrees of crowding problems. Most segmentation approaches presented before are not able to achieve a balance between fine segmentation results and simple operating procedures with less time consumption. In this article, we present a novel, effective and efficient framework that achieves tooth segmentation based on a segmentation field, which is solved by a linear system defined by a discrete Laplace-Beltrami operator with Dirichlet boundary conditions. A set of contour lines are sampled from the smooth scalar field, and candidate cutting boundaries can be detected from concave regions with large variations of field data. The sensitivity to concave seams of the segmentation field facilitates effective tooth partition, as well as avoids obtaining appropriate curvature threshold value, which is unreliable in some case. Our tooth segmentation algorithm is robust to dental models with low quality, as well as is effective to dental models with different levels of crowding problems. The experiments, including segmentation tests of varying dental models with different complexity, experiments on dental meshes with different modeling resolutions and surface noises and comparison between our method and the morphologic skeleton segmentation method are conducted, thus demonstrating the effectiveness of our method. PMID:27532266
Interactive Tooth Separation from Dental Model Using Segmentation Field
2016-01-01
Tooth segmentation on dental model is an essential step of computer-aided-design systems for orthodontic virtual treatment planning. However, fast and accurate identifying cutting boundary to separate teeth from dental model still remains a challenge, due to various geometrical shapes of teeth, complex tooth arrangements, different dental model qualities, and varying degrees of crowding problems. Most segmentation approaches presented before are not able to achieve a balance between fine segmentation results and simple operating procedures with less time consumption. In this article, we present a novel, effective and efficient framework that achieves tooth segmentation based on a segmentation field, which is solved by a linear system defined by a discrete Laplace-Beltrami operator with Dirichlet boundary conditions. A set of contour lines are sampled from the smooth scalar field, and candidate cutting boundaries can be detected from concave regions with large variations of field data. The sensitivity to concave seams of the segmentation field facilitates effective tooth partition, as well as avoids obtaining appropriate curvature threshold value, which is unreliable in some case. Our tooth segmentation algorithm is robust to dental models with low quality, as well as is effective to dental models with different levels of crowding problems. The experiments, including segmentation tests of varying dental models with different complexity, experiments on dental meshes with different modeling resolutions and surface noises and comparison between our method and the morphologic skeleton segmentation method are conducted, thus demonstrating the effectiveness of our method. PMID:27532266
Multilayer model of photon diffusion in skin
Schmitt, J.M.; Zhou, G.X.; Walker, E.C.; Wall, R.T. )
1990-11-01
A diffusion model describing the propagation of photon flux in the epidermal, dermal, and subcutaneous tissue layers of the skin is presented. Assuming that the skin is illuminated by a collimated, finite-aperture source, we develop expressions relating photon flux density within the skin and intensities re-emitted from the skin surface to the optical properties of the individual layers. Model simulations show that the rate at which re-emitted intensities diminish with radial distance away from the source can provide information about absorption and scattering in underlying tissues. Re-emitted intensities measured from homogeneous and two-layer tissue phantoms compare favorably with model predictions. We demonstrate potential applications of the model by estimating the absorption (sigma a) and transport-corrected scattering (sigma's) coefficients of dermis and subcutis from intensities measured from intact skin and by predicting the magnitude of the optical-density variations measured by a photoplethysmograph.
Modelling of the Peltier effect in magnetic multilayers
NASA Astrophysics Data System (ADS)
Juarez-Acosta, Isaac; Olivares-Robles, Miguel A.; Bosu, Subrojati; Sakuraba, Yuya; Kubota, Takahide; Takahashi, Saburo; Takanashi, Koki; Bauer, Gerrit E. W.
2016-02-01
We model the charge, spin, and heat currents in ferromagnetic metal|normal metal|normal metal trilayer structures in the two current model, taking into account bulk and interface thermoelectric properties as well as Joule heating. The results include the temperature distribution as well as resistance-current curves that reproduce the observed shifted parabolic characteristics. Thin tunneling barriers can enhance the apparent Peltier cooling. The model agrees with the experimental results for wide multilayer pillars, but the giant effects observed for diameters ≲100 nm are still under discussion.
Stacked Multilayer Self-Organizing Map for Background Modeling.
Zhao, Zhenjie; Zhang, Xuebo; Fang, Yongchun
2015-09-01
In this paper, a new background modeling method called stacked multilayer self-organizing map background model (SMSOM-BM) is proposed, which presents several merits such as strong representative ability for complex scenarios, easy to use, and so on. In order to enhance the representative ability of the background model and make the parameters learned automatically, the recently developed idea of representative learning (or deep learning) is elegantly employed to extend the existing single-layer self-organizing map background model to a multilayer one (namely, the proposed SMSOM-BM). As a consequence, the SMSOM-BM gains several merits including strong representative ability to learn background model of challenging scenarios, and automatic determination for most network parameters. More specifically, every pixel is modeled by a SMSOM, and spatial consistency is considered at each layer. By introducing a novel over-layer filtering process, we can train the background model layer by layer in an efficient manner. Furthermore, for real-time performance consideration, we have implemented the proposed method using NVIDIA CUDA platform. Comparative experimental results show superior performance of the proposed approach. PMID:25935034
Radon diffusion through multilayer earthen covers: models and simulations
Mayer, D.W.; Oster, C.A.; Nelson, R.W.; Gee, G.W.
1981-09-01
A capability to model and analyze the fundamental interactions that influence the diffusion of radon gas through uranium mill tailings and cover systems has been investigated. The purpose of this study is to develop the theoretical basis for modeling radon diffusion and to develop an understanding of the fundamental interactions that influence radon diffusion. This study develops the theoretical basis for modeling radon diffusion in one, two and three dimensions. The theory has been incorporated into three computer models that are used to analyze several tailings and cover configurations. This report contains a discussion of the theoretical basis for modeling radon diffusion, a discussion of the computer models used to analyze uranium mill tailings and multilayered cover systems, and presents the results that have been obtained.
Modeling of multilayered piezoelectric transducers with ultrasonic welding application
NASA Astrophysics Data System (ADS)
Güney, Murat; Eskinat, Esref
2007-04-01
Mechanical components of sandwiched piezoelectric transducers are modeled using one-dimensional wave transmission and piezoelectric equations. Using the impedance method, resonance frequencies, stress and displacement distributions along the multilayered piezoelectric transducers of different dimensions and materials are obtained. The calculated resonance frequencies and the impedances are experimentally verified. For ultrasonic welding of plastics, the effect of the parts to be welded on the resonance frequency of the whole system is investigated regarding both material damping and piezoelectric losses. Using the methods developed, several piezoelectric transducers are analysed for different designs. The obtained results can be used to better understand the qualitative relations between the design variables of ultrasonic piezoelectric transducers.
Limeback, H
1996-01-01
The above diagnostic and treatment principles may be self evident to most dental practitioners. To many, however, this treatment philosophy is a new one. Continuing dental education and quality assurance programs will play a significant role in helping dentists make the philosophical shift from a highly technical restorative approach to one that uses the medical model and treats dental caries as an infectious disease. While a total cure in humans suffering from dental disease may never be attainable, dental practitioners should soon be better able to direct more of their attention to the patients who already demonstrate a high incidence of dental decay and to those who are clearly at risk to develop future dental decay. PMID:9470624
Finite element modeling of multilayered structures of fish scales.
Chandler, Mei Qiang; Allison, Paul G; Rodriguez, Rogie I; Moser, Robert D; Kennedy, Alan J
2014-12-01
The interlinked fish scales of Atractosteus spatula (alligator gar) and Polypterus senegalus (gray and albino bichir) are effective multilayered armor systems for protecting fish from threats such as aggressive conspecific interactions or predation. Both types of fish scales have multi-layered structures with a harder and stiffer outer layer, and softer and more compliant inner layers. However, there are differences in relative layer thickness, property mismatch between layers, the property gradations and nanostructures in each layer. The fracture paths and patterns of both scales under microindentation loads were different. In this work, finite element models of fish scales of A. spatula and P. senegalus were built to investigate the mechanics of their multi-layered structures under penetration loads. The models simulate a rigid microindenter penetrating the fish scales quasi-statically to understand the observed experimental results. Study results indicate that the different fracture patterns and crack paths observed in the experiments were related to the different stress fields caused by the differences in layer thickness, and spatial distribution of the elastic and plastic properties in the layers, and the differences in interface properties. The parametric studies and experimental results suggest that smaller fish such as P. senegalus may have adopted a thinner outer layer for light-weighting and improved mobility, and meanwhile adopted higher strength and higher modulus at the outer layer, and stronger interface properties to prevent ring cracking and interface cracking, and larger fish such as A. spatula and Arapaima gigas have lower strength and lower modulus at the outer layers and weaker interface properties, but have adopted thicker outer layers to provide adequate protection against ring cracking and interface cracking, possibly because weight is less of a concern relative to the smaller fish such as P. senegalus. PMID:25300062
Light dosimetry for focused and defocused beam irradiation in multi-layered tissue models
NASA Astrophysics Data System (ADS)
Petrova, Kremena S.; Stoykova, Elena V.
2006-09-01
Treatment of acupuncture points, trigger points, joint inflammations in low level laser therapy as well as various applications of lasers for treatment of soft tissues in dental medicine, require irradiation by a narrow converging laser beam. The aim of this study is to compare light delivery produced by focused or defocused narrow beam irradiation in a multi-layered skin tissue model at increasing depth of the target. The task is solved by 3-D Monte-Carlo simulation for matched and mismatched refractive indices at the tissue/ambient medium interface. The modeled light beams have a circular cross-section at the tissue entrance with uniform or Gaussian intensity distribution. Three are the tissue models used in simulation : i) a bloodless skin layer; ii) a bloodless skin layer with embedded scattering object; iii) a skin layer with small blood vessels of varying size, which are modeled as infinite cylinders parallel to the tissue surface located at different depths. Optical properties (absorption coefficient, scattering coefficient, anisotropy factor, g, and index of refraction) of different tissue constituents are chosen from the literature.
Multilayer analytic element modeling of radial collector wells.
Bakker, Mark; Kelson, Victor A; Luther, Kenneth H
2005-01-01
A new multilayer approach is presented for the modeling of ground water flow to radial collector wells. The approach allows for the inclusion of all aspects of the unique boundary condition along the lateral arms of a collector well, including skin effect and internal friction losses due to flow in the arms. The hydraulic conductivity may differ between horizontal layers within the aquifer, and vertical anisotropy can be taken into account. The approach is based on the multilayer analytic element method, such that regional flow and local three-dimensional detail may be simulated simultaneously and accurately within one regional model. Horizontal flow inside a layer is computed analytically, while vertical flow is approximated with a standard finite-difference scheme. Results obtained with the proposed approach compare well to results obtained with three-dimensional analytic element solutions for flow in unconfined aquifers. The presented approach may be applied to predict the yield of a collector well in a regional setting and to compute the origin and residence time, and thus the quality, of water pumped by the collector well. As an example, the addition of three lateral arms to a collector well that already has three laterals is investigated. The new arms are added at an elevation of 2 m above the existing laterals. The yield increase of the collector well is computed as a function of the lengths of the three new arms. PMID:16324013
Multilayer Stock Forecasting Model Using Fuzzy Time Series
Javedani Sadaei, Hossein; Lee, Muhammad Hisyam
2014-01-01
After reviewing the vast body of literature on using FTS in stock market forecasting, certain deficiencies are distinguished in the hybridization of findings. In addition, the lack of constructive systematic framework, which can be helpful to indicate direction of growth in entire FTS forecasting systems, is outstanding. In this study, we propose a multilayer model for stock market forecasting including five logical significant layers. Every single layer has its detailed concern to assist forecast development by reconciling certain problems exclusively. To verify the model, a set of huge data containing Taiwan Stock Index (TAIEX), National Association of Securities Dealers Automated Quotations (NASDAQ), Dow Jones Industrial Average (DJI), and S&P 500 have been chosen as experimental datasets. The results indicate that the proposed methodology has the potential to be accepted as a framework for model development in stock market forecasts using FTS. PMID:24605058
Multilayer stock forecasting model using fuzzy time series.
Javedani Sadaei, Hossein; Lee, Muhammad Hisyam
2014-01-01
After reviewing the vast body of literature on using FTS in stock market forecasting, certain deficiencies are distinguished in the hybridization of findings. In addition, the lack of constructive systematic framework, which can be helpful to indicate direction of growth in entire FTS forecasting systems, is outstanding. In this study, we propose a multilayer model for stock market forecasting including five logical significant layers. Every single layer has its detailed concern to assist forecast development by reconciling certain problems exclusively. To verify the model, a set of huge data containing Taiwan Stock Index (TAIEX), National Association of Securities Dealers Automated Quotations (NASDAQ), Dow Jones Industrial Average (DJI), and S&P 500 have been chosen as experimental datasets. The results indicate that the proposed methodology has the potential to be accepted as a framework for model development in stock market forecasts using FTS. PMID:24605058
Model Teacher - School Dental Hygiene Program.
ERIC Educational Resources Information Center
Smith, Lowell W.
The purpose of this study, which was carried out during the 1972-73 school year at three parochial schools in the Houston area, was to determine the effectiveness of the Toothkeeper Program, a multimedia program of oral hygiene training carefully developed and packaged to establish effective long-term dental hygiene practice. The study population…
Multilayer adsorption model for the protein-ligand interaction
NASA Astrophysics Data System (ADS)
Varela, L. M.; Garcia, M.; Perez-Rodriguez, M.; Taboada, P.; Ruso, J. M.; Mosquera, V.
2001-05-01
In the present work we present a theoretical formalism based on the combination of the Brunauer-Emmet-Teller multilayer adsorption model with an electrolytic adsorbate, and the results are used to predict binding isotherms of several synthetic penicillin drugs onto human serum albumin. The occurrence of adsorption maxima in these binding processes is correctly predicted by this noncooperative binding model and it is demonstrated to be due to the ionic character of the adsorbate. The effect of the hydrophobic interactions between adsorbate monomers on the value of the maximum number of adsorbed particles is also a matter of study, and it is proven that this number increases with increasing hydrophobic character of the adsorbate.
A Reproducible Oral Microcosm Biofilm Model for Testing Dental Materials
Rudney, J.D.; Chen, R.; Lenton, P.; Li, J.; Li, Y.; Jones, R.S.; Reilly, C.; Fok, A.S.; Aparicio, C.
2012-01-01
Aims Most studies of biofilm effects on dental materials use single-species biofilms, or consortia. Microcosm biofilms grown directly from saliva or plaque are much more diverse, but difficult to characterize. We used the Human Oral Microbial Identification Microarray (HOMIM) to validate a reproducible oral microcosm model. Methods and Results Saliva and dental plaque were collected from adults and children. Hydroxyapatite and dental composite disks were inoculated with either saliva or plaque, and microcosm biofilms were grown in a CDC biofilm reactor. In later experiments, the reactor was pulsed with sucrose. DNA from inoculums and microcosms were analyzed by HOMIM for 272 species. Microcosms included about 60% of species from the original inoculum. Biofilms grown on hydroxyapatite and composites were extremely similar. Sucrose-pulsing decreased diversity and pH, but increased the abundance of Streptococcus and Veilonella. Biofilms from the same donor, grown at different times, clustered together. Conclusions This model produced reproducible microcosm biofilms that were representative of the oral microbiota. Sucrose induced changes associated with dental caries. Significance and Impact of the Study This is the first use of HOMIM to validate an oral microcosm model that can be used to study the effects of complex biofilms on dental materials. PMID:22925110
Soil moisture dynamics modeling considering multi-layer root zone.
Kumar, R; Shankar, V; Jat, M K
2013-01-01
The moisture uptake by plant from soil is a key process for plant growth and movement of water in the soil-plant system. A non-linear root water uptake (RWU) model was developed for a multi-layer crop root zone. The model comprised two parts: (1) model formulation and (2) moisture flow prediction. The developed model was tested for its efficiency in predicting moisture depletion in a non-uniform root zone. A field experiment on wheat (Triticum aestivum) was conducted in the sub-temperate sub-humid agro-climate of Solan, Himachal Pradesh, India. Model-predicted soil moisture parameters, i.e., moisture status at various depths, moisture depletion and soil moisture profile in the root zone, are in good agreement with experiment results. The results of simulation emphasize the utility of the RWU model across different agro-climatic regions. The model can be used for sound irrigation management especially in water-scarce humid, temperate, arid and semi-arid regions and can also be integrated with a water transport equation to predict the solute uptake by plant biomass. PMID:23579833
Analytical Modeling of Variable Density Multilayer Insulation for Cryogenic Storage
NASA Technical Reports Server (NTRS)
Hedayat, A.; Hastings, L. J.; Brown, T.; Cruit, Wendy (Technical Monitor)
2001-01-01
A unique foam/Multilayer Insulation (MLI) combination concept for orbital cryogenic storage was experimentally evaluated at NASA Marshall Space Flight Center (MSFC) using the Multipurpose Hydrogen Test Bed (MHTB). The MLI was designed for an on-orbit storage period of 45 days and included several unique features such as: a variable layer density and larger but fewer perforations for venting during ascent to orbit. Test results with liquid hydrogen indicated that the MLI weight or heat leak is reduced by about half in comparison with standard MLI. The focus of this paper is on analytical modeling of the Variable Density MLI (VD-MLI) on-orbit performance (i.e. vacuum/low pressure environment). The foam/VD-MLI combination model is considered to have five segments. The first segment represents the optional foam layer. The second, third, and fourth segments represent three MLI segments with different layer densities. The last segment is considered to be a shroud that surrounds the last MLI layer. Two approaches are considered. In the first approach, the variable density MLI is modeled layer by layer while in the second approach, a semi-empirical model is applied. Both models account for thermal radiation between shields, gas conduction, and solid conduction through the layer separator materials.
The response of the National Oceanic and Atmospheric Administration multilayer inferential dry deposition velocity model (NOAA-MLM) to error in meteorological inputs and model parameterization is reported. Monte Carlo simulations were performed to assess the uncertainty in NOA...
Models for Delivering School-Based Dental Care.
ERIC Educational Resources Information Center
Albert, David A.; McManus, Joseph M.; Mitchell, Dennis A.
2005-01-01
School-based health centers (SBHCs) often are located in high-need schools and communities. Dental service is frequently an addition to existing comprehensive services, functioning in a variety of models, configurations, and locations. SBHCs are indicated when parents have limited financial resources or inadequate health insurance, limiting…
NASA Technical Reports Server (NTRS)
Dumbauld, R. K.; Bjorklund, J. R.; Bowers, J. F.
1973-01-01
The NASA/MSFC multilayer diffusion models are discribed which are used in applying meteorological information to the estimation of toxic fuel hazards resulting from the launch of rocket vehicle and from accidental cold spills and leaks of toxic fuels. Background information, definitions of terms, description of the multilayer concept are presented along with formulas for determining the buoyant rise of hot exhaust clouds or plumes from conflagrations, and descriptions of the multilayer diffusion models. A brief description of the computer program is given, and sample problems and their solutions are included. Derivations of the cloud rise formulas, users instructions, and computer program output lists are also included.
EUV multilayer defect compensation (MDC): latest progress on model and compensation methods
NASA Astrophysics Data System (ADS)
Pang, Linyong; Satake, Masaki; Li, Ying; Hu, Peter; Peng, Danping; Chen, Dongxue; Tolani, Vikram
2013-09-01
Making a multilayer defect-free extreme ultraviolet (EUV) blank is not possible today, and is unlikely to happen in the next few years. The method proposed by Luminescent is to compensate effects of multilayer defects on images by modifying the absorber patterns. Progress in MDC is the subject of this paper. The multilayer growth model was calibrated using real data - the top layer profile captured by AFM and cross section captured by TEM for programmed defects. Multilayer defect profiles on repair sites were recovered by applying inverse methods with the calibrated model to AFM surface scans. The recovered defect profiles were fed into the MDC engine to calculate modified absorber patterns that would compensate for the defects. Further, new methods to compensate for phase errors by depositing materials or peeling multilayers in addition to absorber modifications have been developed. Different options of multilayer peeling for compensating phase error are also evaluated through simulation. A case study was performed to find out what is the maximum pit and bump defects that can be compensated by all options available. It shows absorber pattern modification plus material deposition is the most effective option for pit defect, while absorber pattern modification plus layer-by-layer multilayer peeling is the most effective option for bump defect. Either of these methods can fix defects up to four times larger than those that can be fixed by only modifying absorber patterns near them.
Walsh, M M; Darby, M
1993-01-01
In summary, the theories of Maslow and of Yura and Walsh have been highlighted as background for understanding the human needs conceptual model of dental hygiene. In addition, 11 human needs have been identified and defined as being especially related to dental hygiene care, and a sample evaluation tool for their clinical assessment and a dental hygiene care plan have been presented. The four concepts of client, environment, health/oral health, and dental hygiene actions explained in terms of human need theory, and the 11 human needs related to dental hygiene care constitute the human needs conceptual model of dental hygiene. Within the framework of the human needs conceptual model of dental hygiene, the dental hygiene process is a systematic approach to dental hygiene care that involves assessment of the 11 human needs related to dental hygiene care; analysis of deficits in these needs; determination of the dental hygiene care plan based on identified deficits; implementation of dental hygiene interventions stated in the care plan; and evaluation of the effectiveness of dental hygiene interventions in achieving specific goals, including subsequent reassessment and revision of the dental hygiene care plan. This human needs conceptual model for dental hygiene provides a guide for comprehensive and humanistic client care. This model allows the dental hygienist to view each client (whether an individual or a group) holistically to prevent oral disease and to promote health and wellness. Dental hygiene theorists are encouraged to expand this model or to develop additional conceptual models based on dental hygiene's paradigm. PMID:17233167
The application of multilevel modelling to dental caries data.
Burnside, G; Pine, C M; Williamson, P R
2007-09-30
Clinical studies of dental caries experience generate multiple outcome data for each participant, with information collected for each individual tooth surface. This paper investigates multilevel modelling as a method of analysis for dental caries data, allowing for full use of the data collected at surface level. Data from a clinical trial of a caries preventive agent in adolescents are modelled. The effect of tooth position within the mouth on the development of dental caries is investigated, with the results showing the importance of differentiating between the upper and lower arches, when modelling the probabilities of caries developing on teeth. Calculation of the intracluster correlation using the threshold model is suggested for use in multilevel logistic regression modelling of caries data. This model, which assumes that a dichotomous outcome is based on an underlying continuous variable with a threshold point where the outcome changes from zero to one, is identified to be appropriate for the analysis of caries which is a continuous process, but is only identified as present in a clinical trial when it has reached a certain level of severity. PMID:17340596
A model for forensic dental education in the predoctoral dental school curriculum.
Hermsen, Kenneth P; Johnson, J Dane
2012-05-01
Forensic odontologists play an important role locally and nationally in assisting in the identification of the victims of mass fatality incidents, whether natural or human-made. With the recent passage of legislation by Congress identifying dentists as a first-responder resource, knowledge of their expanding role in disaster response is particularly important. The purpose of this article is to describe the forensic dental course being taught at Creighton University School of Dentistry in Omaha, Nebraska, as a model for providing a fundamental education in forensic dentistry and disaster preparedness at the predoctoral dental level. This model is designed to 1) provide students with a broad view of forensic odontology; 2) give them a functional knowledge of the tools and techniques of the modern forensic dentist; 3) provide basic knowledge of their potential role in disaster preparedness and response; and 4) encourage students to pursue further forensic education, become active in national forensic organizations, and get involved in disaster preparedness/response in their home communities following graduation. This article includes lecture topics, demonstrations, and hands-on exercises being used at Creighton to teach students the fundamentals of forensic odontology and disaster preparedness. PMID:22550101
Simple solutions of multilayered discs subjected to biaxial moment loading.
Hsueh, Chun-Hway; Kelly, J R
2009-01-01
The purpose of this study was to derive a simple closed-form solution for the stress distribution through the thickness of multilayered discs subjected to biaxial moment loading, such that it can be used readily to evaluate the biaxial strength of multilayered dental ceramics using biaxial flexure tests. Methods A simple analytical model was developed to derive the stress distribution through the thickness of multilayered discs subjected to biaxial moment loading. The accuracy of the solution was verified by comparing with previous rigorous analytical solutions and finite element results. The results obtained from Roark's formulas for bilayered discs were also included for comparison.
NASA Astrophysics Data System (ADS)
Stoy, P. C.; Schäfer, K. V.; Katul, G. G.; Oren, R.
2002-05-01
Models of gas exchange are necessary to understand interactions between biosphere and atmosphere, but the effectiveness of multilayer vs. single-layer canopy models is still a matter of debate. Previous studies have discussed benefits and drawbacks of both approaches with reference to one another or have analytically compared single and multilayer models over a single growing season. Here, we critically analyze the performance of both approaches at multiple time scales with respect to 4.5 years of eddy covariance measurement of carbon exchange in a Pinus taeda forest using orthonormal wavelet transformation (OWT). OWT compares model performance at time scales from minutes to years and can identify time scales at which models perform poorly, aiding in the choice between multilayer and single-layer models and identifying areas of model improvement.
NASA/MSFC multilayer diffusion models and computer programs, version 5
NASA Technical Reports Server (NTRS)
Dumbauld, R. K.; Bjorklund, J. R.
1975-01-01
The transport and diffusion models and algorithms developed for use by NASA in predicting concentrations and dosages downwind from normal and abnormal launches of rocket vehicles are described along with the associated computer programs for use in performing the calculations. Topics discussed include: the mathematical specifications and procedures used in the Preprocessor Program to calculate rocket exhaust cloud rise, cloud dimensions, and other input parameters to the transport and diffusion models; the revised mathematical specifications for the Multilayer Diffusion Models; users' instructions for implementing the Preprocessor and Multilayer Diffusion Models Programs; and worked example problems illustrating the use of the models and computer programs.
Nonlinear finite element modeling of dental composite polymerization behavior
NASA Astrophysics Data System (ADS)
Laughlin, Gayle A.
2003-07-01
Polymerization shrinkage has been one of the primary shortcomings preventing the use of resin composites as a universal dental restorative material. This shrinkage of the bonded restoration causes residual stresses in the composite which in turn are transferred to the adhesive interface. The deleterious effects of this stress environment include compromise of the interface itself and the decrease in the mechanical properties of the cured composite. Novel materials which claim to produce less shrinkage have been presented as a new class of restorative materials that could reduce the effects of this problem. One difficulty in assessing the actual in vivo benefits of these new materials is the fact that there is currently no direct way to measure the stress environment at the composite/tooth clinical interface. Computer modeling using finite element analysis (FEA) could provide helpful information regarding the clinical stress performance of dental composites. The purpose of this study was to develop a model that accurately simulates the nonlinear polymerization behavior of light-cured dental composites using a commercial FEA program, which could be accessible for future research. Two phases were needed to accomplish this purpose. First, a data collection phase included volumetric shrinkage, shrinkage stress, tooth analog strain, and dynamic mechanical analysis experiments. Three composites, a standard methacrylate(Z250) and two experimental low stress epoxy-based composites (oxirane and silorane), were tested. The experimental results revealed an intriguing range of polymerization behavior exhibited by the three composites, indicating that the development of a low stress composite is possible. The information gathered from this phase supplied the necessary material input for the computer modeling, and provided empirical validation data for the model solutions. In the second modeling phase, an FEA approach based on a elastic/viscoplastic material model was used to
Metrological validation for 3D modeling of dental plaster casts.
Brusco, Nicola; Andreetto, Marco; Lucchese, Luca; Carmignato, Simone; Cortelazzo, Guido M
2007-11-01
The contribution of this paper is twofold: (1) it presents an automatic 3D modeling technique and (2) it advances a procedure for its metrological evaluation in the context of a medical application, the 3D modeling of dental plaster casts. The motivation for this work is the creation of a "virtual gypsotheque" where cumbersome dental plaster casts can be replaced by numerical 3D models, thereby alleviating storage and access problems and allowing dentists and orthodontists the use of novel and unprecedented software tools for their medical evaluations. Modeling free-form surfaces of anatomical interest is an intriguing mixture of open issues concerning 3D modeling, geometrical metrology, and medicine. Of general interest is both the fact that a widespread use of 3D modeling in non-engineering applications requires automatic procedures of the kind presented in this work and the adopted validation paradigm for free-form surfaces, rather useful for practical purposes. In this latter respect, the metrological analysis we advance is the first seminal attempt in the field of 3D modeling and can be readily extended to contexts other than the medical one discussed in this paper. PMID:17126062
Modeling of light intensification by conical pits within multilayer coatings
Qiu, S R; Wolfe, J E; Monterrosa, A; Feit, M D; Pistor, T V; Stolz, C J
2009-11-02
Removal of laser-induced damage sites provides a possible mitigation pathway to improve damage resistance of coated multilayer dielectric mirrors. In an effort to determine the optimal mitigation geometry which will not generate secondary damage precursors, the electric field distribution within the coating layers for a variety of mitigation shapes under different irradiation angles has been estimated using the finite difference time domain (FDTD) method. The coating consists of twenty-four alternating layers of hafnia and silica with a quarter-wave reflector design. A conical geometrical shape with different cone angles is investigated in the present study. Beam incident angles range from 0{sup o} to 60{sup o} at 5{sup o} increments. We find that light intensification (square of electric field, |E|{sup 2}) within the multilayers depends strongly on the beam incident direction and the cone angle. By comparing the field intensification for each cone angle under all angles of incidence, we find that a 30{sup o} conical pit generates the least field intensification within the multilayer film. Our results suggest that conical pits with shallow cone angles ({le} 30{sup o}) can be used as potential optimal mitigation structures.
A 3-D elasticity theory based model for acoustic radiation from multilayered anisotropic plates.
Shen, C; Xin, F X; Lu, T J
2014-05-01
A theoretical model built upon three-dimensional elasticity theory is developed to investigate the acoustic radiation from multilayered anisotropic plates subjected to a harmonic point force excitation. Fourier transform technique and stationary phase method are combined to predict the far-field radiated sound pressure of one-side water immersed plate. Compared to equivalent single-layer plate models, the present model based on elasticity theory can differentiate radiated sound pressure between dry-side and wet-side excited cases, as well as discrepancies induced by different layer sequences for multilayered anisotropic plates. These results highlight the superiority of the present theoretical model especially for handling multilayered anisotropic structures. PMID:24815294
Developing an Alternative Model for Dental Education.
ERIC Educational Resources Information Center
Rayborn, G. Wayne; And Others
1996-01-01
The restructuring of the oral health sciences program at the University of Alberta (Canada), in response to drastically reduced funding, is described. Major objectives were to reduce program cost to the university and enhance the institution's scholarly/research profile. The model, used in other countries, separates clinical from academic costs.…
Multilayer models in the piezo-PAS analysis of AII-BVI compounds
NASA Astrophysics Data System (ADS)
Maliński, M.; Zakrzewski, J.
2003-01-01
This article presents the results of computations of the photoacoustic piezoelectric spectra, both amplitude and phase, of a series of AII-BVI compounds and their comparison with experimental results. For the interpretation of experimental spectra several multilayer models were developed and applied. Computer analysis showed that it was not possible to interpret the experimental results in the model of a single layer in the case of real samples. In this article three multilayer models are presented and illustrated by experimental results and numerical characteristics.
T.F. Eibert; J.L. Volakis; Y.E. Erdemli
2002-03-03
Hybrid finite element (FE)--boundary integral (BI) analysis of infinite periodic arrays is extended to include planar multilayered Green's functions. In this manner, a portion of the volumetric dielectric region can be modeled via the finite element method whereas uniform multilayered regions can be modeled using a multilayered Green's function. As such, thick uniform substrates can be modeled without loss of efficiency and accuracy. The multilayered Green's function is analytically computed in the spectral domain and the resulting BI matrix-vector products are evaluated via the fast spectral domain algorithm (FSDA). As a result, the computational cost of the matrix-vector products is kept at O(N). Furthermore, the number of Floquet modes in the expansion are kept very few by placing the BI surfaces within the computational unit cell. Examples of frequency selective surface (FSS) arrays are analyzed with this method to demonstrate the accuracy and capability of the approach. One example involves complicated multilayered substrates above and below an inhomogeneous filter element and the other is an optical ring-slot array on a substrate several hundred wavelengths in thickness. Comparisons with measurements are included.
Continuum damage modeling and simulation of hierarchical dental enamel
NASA Astrophysics Data System (ADS)
Ma, Songyun; Scheider, Ingo; Bargmann, Swantje
2016-05-01
Dental enamel exhibits high fracture toughness and stiffness due to a complex hierarchical and graded microstructure, optimally organized from nano- to macro-scale. In this study, a 3D representative volume element (RVE) model is adopted to study the deformation and damage behavior of the fibrous microstructure. A continuum damage mechanics model coupled to hyperelasticity is developed for modeling the initiation and evolution of damage in the mineral fibers as well as protein matrix. Moreover, debonding of the interface between mineral fiber and protein is captured by employing a cohesive zone model. The dependence of the failure mechanism on the aspect ratio of the mineral fibers is investigated. In addition, the effect of the interface strength on the damage behavior is studied with respect to geometric features of enamel. Further, the effect of an initial flaw on the overall mechanical properties is analyzed to understand the superior damage tolerance of dental enamel. The simulation results are validated by comparison to experimental data from micro-cantilever beam testing at two hierarchical levels. The transition of the failure mechanism at different hierarchical levels is also well reproduced in the simulations.
Digital modeling technology for full dental crown tooth preparation.
Dai, Ning; Zhong, Yicheng; Liu, Hao; Yuan, Fusong; Sun, Yuchun
2016-04-01
A dental defect is one of the most common oral diseases, and it often requires a full crown restoration. In this clinical operation, the dentist must manually prepare the affected tooth for the full crown so that it has a convergence angle between 4° and 10°, no undercuts, and uniform and even shoulder widths and depths using a high speed diamond bur in the patient׳s mouth within one hour, which is a difficult task that requires visual-manual operation. The quality of the tooth preparation has an important effect on the success rate of the subsequent prosthodontic treatment. This study involved research into digital modeling technology for full dental crown tooth preparation. First, the margin line of the tooth preparation was designed using a semi-automatic interactive process. Second, the inserting direction was automatically computed. Then, the characteristic parameters and the constraints on the tooth preparation were defined for the model. Next, the shoulder and axial surface of the tooth preparation were formed using parametric modeling. Finally, the implicit surface of a radial basis function was used to construct the tooth preparation׳s occlusal surface. The experimental results verified that the method of digital modeling for full crown preparation proposed in this study can quickly and accurately implement personalized designs of various parameters, such as the shoulder width and the convergence angle; it provides a digital design tool for full crown preparation. PMID:26945598
A mathematical model for the progression of dental caries.
Fabregas, L Rene I; Rubinstein, J
2014-12-01
A model for the progression of dental caries is derived. The analysis starts at the microscopic reaction and diffusion process. The local equations are averaged to derive a set of macroscopic equations. The global system includes features such as anisotropic diffusion and local changes in the geometry due to the melting of the enamel. The equations are then solved numerically. The simulations highlight the effect of anisotropy. In addition, we draw conclusions on the progression rate of caries, and discuss them in light of a number of experiments. PMID:23803287
Multilayer Joint Gait-Pose Manifolds for Human Gait Motion Modeling.
Ding, Meng; Fan, Guolian
2015-11-01
We present new multilayer joint gait-pose manifolds (multilayer JGPMs) for complex human gait motion modeling, where three latent variables are defined jointly in a low-dimensional manifold to represent a variety of body configurations. Specifically, the pose variable (along the pose manifold) denotes a specific stage in a walking cycle; the gait variable (along the gait manifold) represents different walking styles; and the linear scale variable characterizes the maximum stride in a walking cycle. We discuss two kinds of topological priors for coupling the pose and gait manifolds, i.e., cylindrical and toroidal, to examine their effectiveness and suitability for motion modeling. We resort to a topologically-constrained Gaussian process (GP) latent variable model to learn the multilayer JGPMs where two new techniques are introduced to facilitate model learning under limited training data. First is training data diversification that creates a set of simulated motion data with different strides. Second is the topology-aware local learning to speed up model learning by taking advantage of the local topological structure. The experimental results on the Carnegie Mellon University motion capture data demonstrate the advantages of our proposed multilayer models over several existing GP-based motion models in terms of the overall performance of human gait motion modeling. PMID:25532201
NASA Astrophysics Data System (ADS)
Zhu, Y. K.; Yu, Y. G.; Li, L.; Jiang, T.; Wang, X. Y.; Zheng, X. J.
2016-07-01
A Timoshenko beam model combined with piezoelectric constitutive equations and an electrical model was proposed to describe the energy harvesting performances of multilayered d 15 mode PZT-51 piezoelectric bimorphs in series and parallel connections. The effect of different clamped conditions was considered for non-piezoelectric and piezoelectric layers in the theoretical model. The frequency dependences of output peak voltage and power at different load resistances and excitation voltages were studied theoretically, and the results were verified by finite element modeling (FEM) simulation and experimental measurements. Results show that the theoretical model considering different clamped conditions for non-piezoelectric and piezoelectric layers could make a reliable prediction for the energy harvesting performances of multilayered d 15 mode piezoelectric bimorphs. The multilayered d 15 mode piezoelectric bimorph in a series connection exhibits a higher output peak voltage and power than that of a parallel connection at a load resistance of 1 MΩ. A criterion for choosing a series or parallel connection for a multilayered d 15 mode piezoelectric bimorph is dependent on the comparison of applied load resistance with the critical resistance of about 55 kΩ. The proposed model may provide some useful guidelines for the design and performance optimization of d 15 mode piezoelectric energy harvesters.
Jiang, Tingting; Lee, Sang-Mi; Hou, Yanan; Chang, Xin
2016-01-01
Objective To investigate the dimensional accuracy of digital dental models obtained from the dental cone-beam computed tomography (CBCT) scan of alginate impressions according to the time elapse when the impressions are stored under ambient conditions. Methods Alginate impressions were obtained from 20 adults using 3 different alginate materials, 2 traditional alginate materials (Alginoplast and Cavex Impressional) and 1 extended-pour alginate material (Cavex ColorChange). The impressions were stored under ambient conditions, and scanned by CBCT immediately after the impressions were taken, and then at 1 hour intervals for 6 hours. After reconstructing three-dimensional digital dental models, the models were measured and the data were analyzed to determine dimensional changes according to the elapsed time. The changes within the measurement error were regarded as clinically acceptable in this study. Results All measurements showed a decreasing tendency with an increase in the elapsed time after the impressions. Although the extended-pour alginate exhibited a less decreasing tendency than the other 2 materials, there were no statistically significant differences between the materials. Changes above the measurement error occurred between the time points of 3 and 4 hours after the impressions. Conclusions The results of this study indicate that digital dental models can be obtained simply from a CBCT scan of alginate impressions without sending them to a remote laboratory. However, when the impressions are not stored under special conditions, they should be scanned immediately, or at least within 2 to 3 hours after the impressions are taken. PMID:27226958
Gao, Hui; Gao, Jun; Wang, Ling-mei; Wang, Chi
2016-03-01
To satisfy the demand of multilayer films on polarization detection, polarized bidirectional reflectance distribution function of multilayer films on slightly rough substrate is established on the basis of first-order vector perturbation theory and polarization transfer matrix. Due to the function, light scattering polarization properties are studied under multi-factor impacts of two typical targets-monolayer anti-reflection film and multilayer high-reflection films. The result shows that for monolayer anti-reflection film, observing positions have a great influence on the degree of polarization, for the left of the peak increased and right decreased compared with the substrate target. Film target and bare substrate can be distinguished by the degree of polarization in different observation angles. For multilayer high-reflection films, the degree of polarization is significantly associated with the number and optical thickness of layers at different wavelengths of incident light and scattering angles. With the increase of the layer number, the degree of polarization near the mirror reflection area decreases. It reveals that the calculated results coincide with the experimental data, which validates the correctness and rationality of the model. This paper provides a theoretical method for polarization detection of multilayer films target and reflection stealth technology. PMID:27400497
New models of dental education and curricular change: their potential impact on dental education.
Pyle, Marsha A
2012-01-01
The collective body of work over the last seventy-five years in the Journal of Dental Education has chronicled the ongoing critical issues and trends in dental education. The evolution of the curriculum has run in fits and starts across the twentieth century and into the twenty-first. Today, there has been a resurgence in the introspective work of the profession to examine what is taught, how it is taught, in what sequence it is taught, and the context relating dental education to other health professions and the global reach of the educational and professional environment. In the context of contemporary times, individual as well as organizational leadership has refocused the educational environment from teaching to learning. This article discusses the types of curricular changes documented in the Journal of Dental Education. PMID:22262553
NASA Astrophysics Data System (ADS)
Lianhua, Yin
The heat shield of aircraft is made of the major thrusts structure with multilayer thermal insulation part. For protecting against thermo-radiation from larger thrusting force engine,the heat shield is installed around this engine nearby.The multilayer thermal insulation part with multilayer radiation/reflection structure is made of reflection layer and interval layer.At vacuum condition,these materials is higher heat insulation capability than other material,is applied for lots of pats on aircraft extensively.But because of these material is made of metal and nonmetal,it is impossible to receive it's mechanical properties of materials from mechanical tests.These paper describes a new measure of mechanical properties of materials in the heat shield based on model analysis test.At the requirement for the first order lateral frequency,these measure provide for the FEM analysis foundation on the optimization structure of the heat shield.
Modelling self-assembling of colloid particles in multilayered structures
NASA Astrophysics Data System (ADS)
Adamczyk, Zbigniew; Weroński, Paweł; Barbasz, Jakub; Kolasińska, Marta
2007-04-01
Simulations of particle multilayer build-up in the layer by layer (LbL) self-assembling processes have been performed according to the generalized random sequential adsorption (RSA) scheme. The first (precursor) layer having an arbitrary coverage of adsorption centers was generated using the standard RSA scheme pertinent to homogeneous surface. Formation of the consecutive layers (up to 20) was simulated by assuming short-range interaction potentials for two kinds of particles of equal size. Interaction of two particles of different kind resulted in irreversible and localized adsorption upon their contact, whereas particles of the same kind were assumed to interact via the hard potential (no adsorption possible). Using this algorithm theoretical simulations were performed aimed at determining the particle volume fraction as a function of the distance from the interface, as well as the multilayer film roughness and thickness as a function of the number of layers. The simulations revealed that particle concentration distribution in the film was more uniform for low precursor layer density than for higher density, where well-defined layers of closely packed particles appeared. On the other hand, the roughness of the film was the lowest at the highest precursor layer density. It was also predicted theoretically that for low precursor layer density the film thickness increased with the number of layers in a non-linear way. However, for high precursor layer density, the film thickness increased linearly with the number of layers and the average layer thickness was equal to 1.58 of the particle radius, which is close to the closely packed hexagonal layer thickness equal to 1.73. It was concluded by analysing the existing data for colloid particles and polyelectrolytes that the theoretical results can be effectively exploited for interpretation of the LbL processes involving colloid particles and molecular species like polymers or proteins.
Beam-tracing model for predicting sound fields in rooms with multilayer bounding surfaces
NASA Astrophysics Data System (ADS)
Wareing, Andrew; Hodgson, Murray
2005-10-01
This paper presents the development of a wave-based room-prediction model for predicting steady-state sound fields in empty rooms with specularly reflecting, multilayer surfaces. A triangular beam-tracing model with phase, and a transfer-matrix approach to model the surfaces, were involved. Room surfaces were modeled as multilayers of fluid, solid, or porous materials. Biot theory was used in the transfer-matrix formulation of the porous layer. The new model consisted of the transfer-matrix model integrated into the beam-tracing algorithm. The transfer-matrix model was validated by comparing predictions with those by theory, and with experiment. The test surfaces were a glass plate, double drywall panels, double steel panels, a carpeted floor, and a suspended-acoustical ceiling. The beam-tracing model was validated in the cases of three idealized room configurations-a small office, a corridor, and a small industrial workroom-with simple boundary conditions. The number of beams, the reflection order, and the frequency resolution required to obtain accurate results were investigated. Beam-tracing predictions were compared with those by a method-of-images model with phase. The model will be used to study sound fields in rooms with local- or extended-reaction multilayer surfaces.
Testing and numerical modeling of hypervelocity impact damaged Space Station multilayer insulation
NASA Technical Reports Server (NTRS)
Rule, William K.
1992-01-01
Results are presented of experiments measuring the degradation of the insulating capabilities of the multilayer insulation (MLI) of the Space Station Freedom, when subjected to hypervelocity impact damage. A simple numerical model was developed for use in an engineering design environment for quick assessment of thermal effect of the impact. The model was validated using results from thermal vacuum tests on MLI with simulated damage. The numerical model results agreed with experimental data.
Herrera-May, Agustín L.; Aguilera-Cortés, Luz A.; Plascencia-Mora, Hector; Rodríguez-Morales, Ángel L.; Lu, Jian
2011-01-01
Multilayered microresonators commonly use sensitive coating or piezoelectric layers for detection of mass and gas. Most of these microresonators have a variable cross-section that complicates the prediction of their fundamental resonant frequency (generally of the bending mode) through conventional analytical models. In this paper, we present an analytical model to estimate the first resonant frequency and deflection curve of single-clamped multilayered microresonators with variable cross-section. The analytical model is obtained using the Rayleigh and Macaulay methods, as well as the Euler-Bernoulli beam theory. Our model is applied to two multilayered microresonators with piezoelectric excitation reported in the literature. Both microresonators are composed by layers of seven different materials. The results of our analytical model agree very well with those obtained from finite element models (FEMs) and experimental data. Our analytical model can be used to determine the suitable dimensions of the microresonator’s layers in order to obtain a microresonator that operates at a resonant frequency necessary for a particular application. PMID:22164071
Modeling Multilayer Antireflection Coating Systems Based on LiNbO3
NASA Astrophysics Data System (ADS)
Karaomerlioglu, Filiz
Antireflection coatings have had the greatest impact on optics. The antireflection (AR) coating is the critically important technology in obtaining high performance of optoelectronic devices. In the present paper, characteristics of the ferroelectric based multilayered antireflection coating systems are investigated. Multilayer antireflection coatings consisting of insulator thin films have been modeled in the region between the 400 nm and 800 nm visible bands of electromagnetic spectrum to reduce reflectance from ferroelectric based substrate. In this type of antireflection coating we can regulate the optical properties of a system by external electric (or thermal field) and design a broadband low reflection coating system for optoelectronic devices. In order to design and simulate the normal incidence wideband visible multilayer AR coatings, we have developed a Fortran software program based upon Fresnell equations. Different types of layers which are two-different materials like ZnSe and ZrO2 for even-folded multilayer (two-, four-, six-, eight-, ten-, and twelve-layer) antireflection coatings are used. Ferroelectric material, LiNbO3 is used as the substrate. The optical thicknesses of each layer are equal to a quarter-wave thick at a certain wavelength.
Use and Application of Structural Models in Dental Education Research.
ERIC Educational Resources Information Center
Potter, Rosario H. Yap; McDonald, Ralph E.
1985-01-01
Latent abilities of dental students were analyzed as causes and professional achievements as effects, with preadmission performances as indicators of latent abilities. The results demonstrate that structural analysis focuses on the direct impact of the quality of dental school education. (Author/MLW)
A General Reliability Model for Ni-BaTiO3-Based Multilayer Ceramic Capacitors
NASA Technical Reports Server (NTRS)
Liu, Donhang
2014-01-01
The evaluation of multilayer ceramic capacitors (MLCCs) with Ni electrode and BaTiO3 dielectric material for potential space project applications requires an in-depth understanding of their reliability. A general reliability model for Ni-BaTiO3 MLCC is developed and discussed. The model consists of three parts: a statistical distribution; an acceleration function that describes how a capacitor's reliability life responds to the external stresses, and an empirical function that defines contribution of the structural and constructional characteristics of a multilayer capacitor device, such as the number of dielectric layers N, dielectric thickness d, average grain size, and capacitor chip size A. Application examples are also discussed based on the proposed reliability model for Ni-BaTiO3 MLCCs.
NASA Astrophysics Data System (ADS)
Bedane, T.; Di Maio, L.; Scarfato, P.; Incarnato, L.; Marra, F.
2015-12-01
The barrier performance of multilayer polymeric films for food applications has been significantly improved by incorporating oxygen scavenging materials. The scavenging activity depends on parameters such as diffusion coefficient, solubility, concentration of scavenger loaded and the number of available reactive sites. These parameters influence the barrier performance of the film in different ways. Virtualization of the process is useful to characterize, design and optimize the barrier performance based on physical configuration of the films. Also, the knowledge of values of parameters is important to predict the performances. Inverse modeling and sensitivity analysis are sole way to find reasonable values of poorly defined, unmeasured parameters and to analyze the most influencing parameters. Thus, the objective of this work was to develop a model to predict barrier properties of multilayer film incorporated with reactive layers and to analyze and characterize their performances. Polymeric film based on three layers of Polyethylene terephthalate (PET), with a core reactive layer, at different thickness configurations was considered in the model. A one dimensional diffusion equation with reaction was solved numerically to predict the concentration of oxygen diffused into the polymer taking into account the reactive ability of the core layer. The model was solved using commercial software for different film layer configurations and sensitivity analysis based on inverse modeling was carried out to understand the effect of physical parameters. The results have shown that the use of sensitivity analysis can provide physical understanding of the parameters which highly affect the gas permeation into the film. Solubility and the number of available reactive sites were the factors mainly influencing the barrier performance of three layered polymeric film. Multilayer films slightly modified the steady transport properties in comparison to net PET, giving a small reduction
Bedane, T.; Di Maio, L.; Scarfato, P.; Incarnato, L. Marra, F.
2015-12-17
The barrier performance of multilayer polymeric films for food applications has been significantly improved by incorporating oxygen scavenging materials. The scavenging activity depends on parameters such as diffusion coefficient, solubility, concentration of scavenger loaded and the number of available reactive sites. These parameters influence the barrier performance of the film in different ways. Virtualization of the process is useful to characterize, design and optimize the barrier performance based on physical configuration of the films. Also, the knowledge of values of parameters is important to predict the performances. Inverse modeling and sensitivity analysis are sole way to find reasonable values of poorly defined, unmeasured parameters and to analyze the most influencing parameters. Thus, the objective of this work was to develop a model to predict barrier properties of multilayer film incorporated with reactive layers and to analyze and characterize their performances. Polymeric film based on three layers of Polyethylene terephthalate (PET), with a core reactive layer, at different thickness configurations was considered in the model. A one dimensional diffusion equation with reaction was solved numerically to predict the concentration of oxygen diffused into the polymer taking into account the reactive ability of the core layer. The model was solved using commercial software for different film layer configurations and sensitivity analysis based on inverse modeling was carried out to understand the effect of physical parameters. The results have shown that the use of sensitivity analysis can provide physical understanding of the parameters which highly affect the gas permeation into the film. Solubility and the number of available reactive sites were the factors mainly influencing the barrier performance of three layered polymeric film. Multilayer films slightly modified the steady transport properties in comparison to net PET, giving a small reduction
Reduction of fear-related dental management problems with use of filmed modeling.
Melamed, B G; Weinstein, D; Katin-Borland, M; Hawes, R
1975-04-01
In this study of the modification of anxiety-related disruptive behavior in dental treatment, matched groups of inner-city children attending a pedodontic clinic were shown a videotaped demonstration of a 4-year-old black child undergoing a dental restorative procedure or were given an unrelated drawing task before dental treatment. Children who viewed the videotape demonstration of a peer model coping with dental procedures showed significantly fewer fear-related disruptive behaviors during restoration of lesions. Observations of children's anxiety levels made by dentists and independent observers validated the effectiveness of viewing the videotaped demonstration. No significant correlation was found between the children's reports of their anxiety and their behavior during dental treatment. PMID:123932
ERIC Educational Resources Information Center
Conyers, Carole; Miltenberger, Raymond G.; Peterson, Blake; Gubin, Amber; Jurgens, Mandy; Selders, Andrew; Dickinson, Jessica; Barenz, Rebecca
2004-01-01
Fear of dental procedures deters many individuals with mental retardation from accepting dental treatment. This study was conducted to assess the effectiveness of two procedures, in vivo desensitization and video modeling, for increasing compliance with dental procedures in participants with severe or profound mental retardation. Desensitization…
Modeling of the Thermal Protection of a Multilayer Material Under Fire Conditions
NASA Astrophysics Data System (ADS)
Ovchinnikov, V. A.; Yakimov, A. S.
2016-06-01
On the basis of the theoretical and known experimental results, a refined mathematical model of the thermochemical destruction of a multilayer heat-shield coating has been developed. Account of the flow across the body has made it possible to forecast more exactly the state of the protected structure under fire conditions. A comparison between the results of numerical calculations and the known data has been made.
Modeling of the Thermal Protection of a Multilayer Material Under Fire Conditions
NASA Astrophysics Data System (ADS)
Ovchinnikov, V. A.; Yakimov, A. S.
2016-05-01
On the basis of the theoretical and known experimental results, a refined mathematical model of the thermochemical destruction of a multilayer heat-shield coating has been developed. Account of the flow across the body has made it possible to forecast more exactly the state of the protected structure under fire conditions. A comparison between the results of numerical calculations and the known data has been made.
Multi-layer model of correlated energy prices
NASA Astrophysics Data System (ADS)
Grine, Slimane; Diko, Pavel
2010-03-01
In this article we develop an extension of the affine jump-diffusion modeling framework and use it to build an intuitive and tractable model of an energy price complex. The development is motivated by the need to model prices of electricity while capturing their dependence on the price of other energy commodities. Such a model is essential for valuing a range of typical derivatives traded in the electricity markets: cross-commodity spread options, cross-location spread options, fuel-switching powerplants, etc. We give an approximate pricing method for these derivatives together with precise error bound estimates.
Material parameter computation for multi-layered vocal fold models
Schmidt, Bastian; Stingl, Michael; Leugering, Günter; Berry, David A.; Döllinger, Michael
2011-01-01
Today, the prevention and treatment of voice disorders is an ever-increasing health concern. Since many occupations rely on verbal communication, vocal health is necessary just to maintain one’s livelihood. Commonly applied models to study vocal fold vibrations and air flow distributions are self sustained physical models of the larynx composed of artificial silicone vocal folds. Choosing appropriate mechanical parameters for these vocal fold models while considering simplifications due to manufacturing restrictions is difficult but crucial for achieving realistic behavior. In the present work, a combination of experimental and numerical approaches to compute material parameters for synthetic vocal fold models is presented. The material parameters are derived from deformation behaviors of excised human larynges. The resulting deformations are used as reference displacements for a tracking functional to be optimized. Material optimization was applied to three-dimensional vocal fold models based on isotropic and transverse-isotropic material laws, considering both a layered model with homogeneous material properties on each layer and an inhomogeneous model. The best results exhibited a transversal-isotropic inhomogeneous (i.e., not producible) model. For the homogeneous model (three layers), the transversal-isotropic material parameters were also computed for each layer yielding deformations similar to the measured human vocal fold deformations. PMID:21476672
NASA Astrophysics Data System (ADS)
Hoi, K. I.; Yuen, K. V.; Mok, K. M.
2013-09-01
Multilayer perceptron (MLP), normally trained by the offline backpropagation algorithm, could not adapt to the changing air quality system and subsequently underperforms. To improve this, the extended Kalman filter is adopted into the learning algorithm to build a time-varying multilayer perceptron (TVMLP) in this study. Application of the TVMLP to model the daily averaged concentration of the respirable suspended particulates with aerodynamic diameter of not more than 10 µm (PM10) in Macau shows statistically significant improvement on the performance indicators over the MLP counterpart. In addition, the adaptive learning algorithm could also address explicitly the uncertainty of the prediction so that confidence intervals can be provided. More importantly, the adaptiveness of the TVMLP gives prediction improvement on the region of higher particulate concentrations that the public concerns.
NASA Astrophysics Data System (ADS)
Chen, Yu-Yi; Juang, Jia-Yang
2016-07-01
The standard collinear four-point probe method is an indispensable tool and has been extensively used for characterizing conductive thin films with homogeneous and isotropic electrical properties. In this paper, we conduct three-dimensional (3D) finite element simulations on conductive multilayer films to study the relationship between the reading of the four-point probe and the conductivity of the individual layers. We find that a multilayer film may be modeled as a simple equivalent circuit with multiple resistances, connected in parallel for a wide range of resistivity and thickness ratios, as long as its total thickness is smaller than approximately half of the probe spacing. As a result, we may determine the resistivity of each layer sequentially by applying the four-point probe, with the original correction factor π/ln(2), after deposition of each layer.
Modeling of Multi-Layered Protection Systems for Chloride Penetration in Concrete Bridge Decks
NASA Astrophysics Data System (ADS)
Harajli, Ali A.
Modeling of Multi-Layered Protection Systems for Chloride Penetration in Concrete Bridge Decks. This paper covers the development of a new methodology for predicting the chloride concentration and corrosion initiation times for a multi-layer protection overlay system. The first topic will be presenting an innovative method to predict the chloride concentrations using different diffusion coefficients for each protective layer. The new method covers the cases where the applied surface chloride concentrations are either a constant or linear functions with time. The second topic will implement the results from field data about the chloride variations due to the presence of applied topical layers for comparison with the theoretical models. This section will also apply damage factors that are time-dependent to simulate external factors such as traffic loading or vibrations. The third topic will investigate the sensitivity of the single and multi-layer systems due to diffusivity parameter changes. The fourth topic will analyze the random variation of the diffusivity values to predict the mean and standard deviation of chloride concentrations. The diffusivity values are selected from published values by NIST and are based on certain water cement (w/c) ratios.
The feature-based modeling of standard tooth in a dental prosthetic database.
Song, Ya-Li; Li, Jia; Huang, Tian; Gao, Ping
2005-01-01
This paper presents a feature-based approach that creates standard teeth models in database to provide the topological construction of the model for dental CAD. The approach arises from the basic idea that every tooth has its individual features and can be implemented in three steps. In the first step, the features on teeth are defined according to the oral anatomy. In the second step, Nurbs surfaces are applied so that the forms of standard teeth can be represented via establishing the topological relationship of features. Here, these feature-based surfaces have the capability of being local controlled that guarantees the accuracy of dental design. In the last step, feature curves are presented to describe the topological construction of dental ridges and grooves. Through these curves, the occlusal surface can be changed globally, simplifying dental design. It is finished with the establishment of standard database composed of 28 standard models constructed by feature-based surfaces and feature curves. PMID:17281869
Advertising, Consensus, and Aging in Multilayer Sznajd Model
NASA Astrophysics Data System (ADS)
Schulze, Christian
In the Sznajd consensus model on the square lattice, two people who agree in their opinions convince their neighbors of this opinion. We generalize it to many layers representing many age levels, and check if a consensus among all layers is possible. Advertising sometimes, but not always, produces a consensus on the advertised opinion.
NASA Astrophysics Data System (ADS)
Monier-Vinard, Eric; Laraqi, Najib; Dia, Cheikh-Tidiane; Nguyen, Minh-Nhat; Bissuel, Valentin
2015-01-01
Electronic components are continuously getting smaller and embedding more and more powered functions which exacerbate the temperature rise in component/board interconnect areas. For still air conditions, the heat spreading of the component power is mainly done through the surrounding metallic planes of its electronic board. Their design optimization is henceforth mandatory to control the temperature and to preserve component reliability. To allow the electronic designer to early analyze the limits of the power dissipation of miniaturized devices, an analytical model of a multi-layered electronic board was established with the purpose to assess the validity of conventional board modeling approach. For decades, numerous authors have been promoting a homogenous single layer model that summed up the layers of the board using effective orthotropic thermal properties. The derived compact model depends on thermal properties approximation which is commonly based on parallel conduction model given a linear rule of mixture. The work presents the thermal behavior comparison of a detailed multi-layer representation to its deducted compact model for an extensive set of variable parameters, such as heat transfer coefficients, effective thermal conductivities calculation models, number of trace layers, trace coverage or source size. The results highlight the fact that the conventional practices for PCB modeling can dramatically underestimate source temperatures when their size is getting very small.
Inverse Monte Carlo method in a multilayered tissue model for diffuse reflectance spectroscopy.
Fredriksson, Ingemar; Larsson, Marcus; Strömberg, Tomas
2012-04-01
Model based data analysis of diffuse reflectance spectroscopy data enables the estimation of optical and structural tissue parameters. The aim of this study was to present an inverse Monte Carlo method based on spectra from two source-detector distances (0.4 and 1.2 mm), using a multilayered tissue model. The tissue model variables include geometrical properties, light scattering properties, tissue chromophores such as melanin and hemoglobin, oxygen saturation and average vessel diameter. The method utilizes a small set of presimulated Monte Carlo data for combinations of different levels of epidermal thickness and tissue scattering. The path length distributions in the different layers are stored and the effect of the other parameters is added in the post-processing. The accuracy of the method was evaluated using Monte Carlo simulations of tissue-like models containing discrete blood vessels, evaluating blood tissue fraction and oxygenation. It was also compared to a homogeneous model. The multilayer model performed better than the homogeneous model and all tissue parameters significantly improved spectral fitting. Recorded in vivo spectra were fitted well at both distances, which we previously found was not possible with a homogeneous model. No absolute intensity calibration is needed and the algorithm is fast enough for real-time processing. PMID:22559695
Modelling the Longevity of Dental Restorations by means of a CBR System
Aliaga, Ignacio J.; Vera, Vicente; García, Alvaro E.
2015-01-01
The lifespan of dental restorations is limited. Longevity depends on the material used and the different characteristics of the dental piece. However, it is not always the case that the best and longest lasting material is used since patients may prefer different treatments according to how noticeable the material is. Over the last 100 years, the most commonly used material has been silver amalgam, which, while very durable, is somewhat aesthetically displeasing. Our study is based on the collection of data from the charts, notes, and radiographic information of restorative treatments performed by Dr. Vera in 1993, the analysis of the information by computer artificial intelligence to determine the most appropriate restoration, and the monitoring of the evolution of the dental restoration. The data will be treated confidentially according to the Organic Law 15/1999 on 13 December on the Protection of Personal Data. This paper also presents a clustering technique capable of identifying the most significant cases with which to instantiate the case-base. In order to classify the cases, a mixture of experts is used which incorporates a Bayesian network and a multilayer perceptron; the combination of both classifiers is performed with a neural network. PMID:25866792
In Vitro Evaluation of New Approach to Digital Dental Model Articulation
Chang, Yu-Bing; Xia, James J.; Gateno, Jaime; Xiong, Zixiang; Teichgraeber, John F.; Lasky, Robert E.; Zhou, Xiaobo
2015-01-01
Purpose The purpose of the present study was to evaluate the accuracy of our newly developed approach to digital dental model articulation. Materials and Methods Twelve sets of stone dental models from patients with craniomaxillofacial deformities were used for validation. All the models had stable occlusion and no evidence of early contact. The stone models were hand articulated to the maximal intercuspation (MI) position and scanned using a 3-dimensional surface laser scanner. These digital dental models at the MI position served as the control group. To establish an experimental group, each mandibular dental model was disarticulated from its original MI position to 80 initial positions. Using a regular office personal computer, they were digitally articulated to the MI position using our newly developed approach. These rearticulated mandibular models served as the experimental group. Finally, the translational, rotational, and surface deviations in the mandibular position were calculated between the experimental and control groups, and statistical analyses were performed. Results All the digital dental models were successfully articulated. Between the control and experimental groups, the largest translational difference in mandibular position was within 0.2 mm ± 0.6 mm. The largest rotational difference was within 0.1° ± 1.1°. The averaged surface deviation was 0.08 ± 0.07. The results of the Bland and Altman method of assessing measurement agreement showed tight limits for the translational, rotational, and surface deviations. In addition, the final positions of the mandibular articulated from the 80 initial positions were absolutely agreed on. Conclusion The results of our study have demonstrated that using our approach, the digital dental models can be accurately and effectively articulated to the MI position. In addition, the 3-dimensional surface geometry of the mandibular teeth played a more important role in digital dental articulation than the
Arcjet Testing and Thermal Model Development for Multilayer Felt Reusable Surface Insulation
NASA Technical Reports Server (NTRS)
Milos, Frank S.; Scott, Carl Douglas; Papa, Steven V.
2012-01-01
Felt Reusable Surface Insulation was used extensively on leeward external surfaces of the Shuttle Orbiter, where the material is reusable for temperatures up to 670 K. For application on leeward surfaces of the Orion Multi-Purpose Crew Vehicle, where predicted temperatures reach 1620 K, the material functions as a pyrolyzing conformal ablator. An arcjet test series was conducted to assess the performance of multilayer Felt Reusable Surface Insulation at high temperatures, and a thermal-response, pyrolysis, and ablation model was developed. Model predictions compare favorably with the arcjet test data
Mass Conservation in Modeling Moisture Diffusion in Multi-Layer Carbon Composite Structures
NASA Technical Reports Server (NTRS)
Nurge, Mark A.; Youngquist, Robert C.; Starr, Stanley O.
2009-01-01
Moisture diffusion in multi-layer carbon composite structures is difficult to model using finite difference methods due to the discontinuity in concentrations between adjacent layers of differing materials. Applying a mass conserving approach at these boundaries proved to be effective at accurately predicting moisture uptake for a sample exposed to a fixed temperature and relative humidity. Details of the model developed are presented and compared with actual moisture uptake data gathered over 130 days from a graphite epoxy composite sandwich coupon with a Rohacell foam core.
Continuum damage model for ferroelectric materials and its application to multilayer actuators
NASA Astrophysics Data System (ADS)
Gellmann, Roman; Ricoeur, Andreas
2016-05-01
In this paper a micromechanical continuum damage model for ferroelectric materials is presented. As a constitutive law it is implemented into a finite element (FE) code. The model is based on micromechanical considerations of domain switching and its interaction with microcrack growth and coalescence. A FE analysis of a multilayer actuator is performed, showing the initiation of damage zones at the electrode tips during the poling process. Further, the influence of mechanical pre-stressing on damage evolution and actuating properties is investigated. The results provided in this work give useful information on the damage of advanced piezoelectric devices and their optimization.
NASA Astrophysics Data System (ADS)
Fernández-Nieto, E. D.; Garres-Díaz, J.; Mangeney, A.; Narbona-Reina, G.
2016-07-01
In this work we present a multilayer shallow model to approximate the Navier-Stokes equations with hydrostatic pressure and the $\\mu(I)$-rheology. The main advantages of this approximation are (i) the low cost associated with the numerical treatment of the free surface of the modelled flows, (ii) exact conservation of mass and (iii) the ability to compute 3D profiles of the velocities in the directions along and normal to the slope. The derivation of the model follows [14] and introduces a dimensional analysis based on the shallow flow hypothesis. The proposed first order multilayer model fully satisfies a dissipative energy equation. A comparison with an analytical solution with a non-constant normal profile of the downslope velocity demonstrates the accuracy of the numerical model. Finally, by comparing the numerical results with experimental data, we show that the proposed multilayer model with the $\\mu(I)$-rheology reproduces qualitatively the effect of the erodible bed on granular flow dynamics and deposits, such as the increase of runout distance with increasing thickness of the erodible bed. We show that the use of a constant friction coefficient in the multilayer model leads to the opposite behaviour. This multilayer model captures the different normal profiles of the downslope velocity during the different phases of the flow (acceleration, stopping, etc.) including the presence of static and flowing zones within the granular column.
FPGA Implementation of Multilayer Perceptron for Modeling of Photovoltaic panel
Mekki, H.; Belhout, K.; Mellit, A.; Salhi, H.
2008-06-12
The Number of electronic applications using artificial neural network-based solutions has increased considerably in the last few years. However, their applications in photovoltaic systems are very limited. This paper introduces the preliminary result of the modeling and simulation of photovoltaic panel based on neural network and VHDL-language. In fact, an experimental database of meteorological data (irradiation, temperature) and output electrical generation signals of the PV-panel (current and voltage) has been used in this study. The inputs of the ANN-PV-panel are the daily total irradiation and mean average temperature while the outputs are the current and voltage generated from the panel. Firstly, a dataset of 4x364 have been used for training the network. Subsequently, the neural network (MLP) corresponding to PV-panel is simulated using VHDL language based on the saved weights and bias of the network. Simulation results of the trained MLP-PV panel based on Matlab and VHDL are presented. The proposed PV-panel model based ANN and VHDL permit to evaluate the performance PV-panel using only the environmental factors and involves less computational efforts, and it can be used for predicting the output electrical energy from the PV-panel.
Modeling of the photodetector based on the multilayer graphene nanoribbons
NASA Astrophysics Data System (ADS)
Liu, Haiyue; Niu, Yanxiong; Yin, Yiheng; Liu, Shuai
2016-07-01
Graphene nanoribbon (GNR), which has unique properties and advantages, is a crucial component of nanoelectornic devices, especially in the development of photoelectric detectors. In this work, an infrared photodetector based on the structure of stacked multiple-GNRs, which is separated by a little thick barrier layers (made of tungsten disulfide or related materials) to prevent tunneling current, is proposed and modeled. Operation of photoelectric detector is related to the electron cascaded radiative transition in the adjacent GNRs strengthened by the electrons heated due to the incident light. With a developed model, the working principle is analyzed and the relationships for the photocurrent and dark current as functions of the intensity of the incident radiation are derived. The spectral dependence of the responsivity and detectivity for graphene nanoribbons photodetector (GNRs-PT) with different Fermi energy, band gaps and numbers of GNRs layers are analyzed as well. The results demonstrate that the spectral characteristics depend on the GNRs band gap, which shows a potential on GNRs-PT application in the multi-wavelength systems. In addition, GNRs-PT has a better spectrum property and higher responsivity compared to photodetectors based on InxGaxAs in room temperature.
Density functional theory modeling of multilayer "epitaxial" graphene oxide.
Zhou, Si; Bongiorno, Angelo
2014-11-18
CONSPECTUS: Graphene oxide (GO) is a complex material of both fundamental and applied interest. Elucidating the structure of GO is crucial to achieve control over its properties and technological applications. GO is a nonstoichiometric and hygroscopic material with a lamellar structure, and its physical chemical properties depend critically on synthesis procedures and postsynthesis treatments. Numerous efforts are in place to both understand and exploit this versatile layered carbon material. This Account reports on recent density functional theory (DFT) studies of "epitaxial" graphene oxide (hereafter EGO), a type of GO obtained by oxidation of graphene films grown epitaxially on silicon carbide. Here, we rely on selected X-ray photoelectron spectroscopy (XPS), infrared spectroscopy (IR), and X-ray diffraction (XRD) measurements of EGO, and we discuss in great detail how we utilized DFT-based techniques to project out from the experimental data basic atomistic information about the chemistry and structure of these films. This Account provides an example as to how DFT modeling can be used to elucidate complex materials such as GO from a limited set of experimental information. EGO exhibits a uniform layered structure, consisting of a stack of graphene planes hosting predominantly epoxide and hydroxyl groups, and water molecules intercalated between the oxidized carbon layers. Here, we first focus on XPS measurements of EGO, and we use DFT to generate realistic model structures, calculate core-level chemical shifts, and through the comparison with experiment, gain insight on the chemical composition and metastability characteristics of EGO. DFT calculations are then used to devise a simplistic but accurate simulation scheme to study thermodynamic and kinetic stability and to predict the intralayer structure of EGO films aged at room temperature. Our simulations show that aged EGO encompasses layers with nanosized oxidized domains presenting a high concentration of
Multilayer Markov Random Field models for change detection in optical remote sensing images
NASA Astrophysics Data System (ADS)
Benedek, Csaba; Shadaydeh, Maha; Kato, Zoltan; Szirányi, Tamás; Zerubia, Josiane
2015-09-01
In this paper, we give a comparative study on three Multilayer Markov Random Field (MRF) based solutions proposed for change detection in optical remote sensing images, called Multicue MRF, Conditional Mixed Markov model, and Fusion MRF. Our purposes are twofold. On one hand, we highlight the significance of the focused model family and we set them against various state-of-the-art approaches through a thematic analysis and quantitative tests. We discuss the advantages and drawbacks of class comparison vs. direct approaches, usage of training data, various targeted application fields and different ways of Ground Truth generation, meantime informing the Reader in which roles the Multilayer MRFs can be efficiently applied. On the other hand we also emphasize the differences between the three focused models at various levels, considering the model structures, feature extraction, layer interpretation, change concept definition, parameter tuning and performance. We provide qualitative and quantitative comparison results using principally a publicly available change detection database which contains aerial image pairs and Ground Truth change masks. We conclude that the discussed models are competitive against alternative state-of-the-art solutions, if one uses them as pre-processing filters in multitemporal optical image analysis. In addition, they cover together a large range of applications, considering the different usage options of the three approaches.
NASA Astrophysics Data System (ADS)
Blažević, D.; Zelenika, S.
2015-05-01
Scavenging of low-level ambient vibrations i.e. the conversion of kinetic into electric energy, is proven as effective means of powering low consumption electronic devices such as wireless sensor nodes. Cantilever based scavengers are characterised by several advantages and thus thoroughly investigated; analytical models based on a distributed parameter approach, Euler-Bernoulli beam theory and eigenvalue analysis have thus been developed and experimentally verified. Finite element models (FEM) have also been proposed employing different modelling approaches and commercial software packages with coupled analysis capabilities. An approach of using a FEM analysis of a piezoelectric cantilever bimorph under harmonic excitation is used in this work. Modal, harmonic and linear and nonlinear transient analyses are performed. Different complex dynamic effects are observed and compared to the results obtained by using a distributed parameter model. The influence of two types of finite elements and three mesh densities is also investigated. A complex bimorph cantilever, based on commercially available Midé Technology® Volture energy scavengers, is then considered. These scavengers are characterised by an intricate multilayer structure not investigated so far in literature. An experimental set-up is developed to evaluate the behaviour of the considered class of devices. The results of the modal and the harmonic FEM analyses of the behaviour of the multilayer scavengers are verified experimentally for three different tip masses and 12 different electrical load values. A satisfying agreement between numerical and experimental results is achieved.
Accuracy of lumped-parameter representations for heat conduction modeling in multilayer slabs
NASA Astrophysics Data System (ADS)
Gori, Paola; Guattari, Claudia; de Lieto Vollaro, Roberto; Evangelisti, Luca
2015-11-01
Heat conduction in homogeneous solids can be studied by resorting to one-dimensional schemes, as is often done, e.g., for building construction elements. In such situations, a simple model often employed makes use of an electrical analogy between temperature and heat flux, on one side, and voltage and electrical current on the other side. Within this framework, a few lumped-parameter representations have been described in literature to describe the thermal behavior of a single homogeneous slab or of multilayer slabs. Such models have the advantage of providing some physical insight into the phenomenon of one-dimensional heat conduction, by conveying the concepts of thermal resistance and thermal capacitance, the latter related to heat storage ability. There is, however, a certain degree of approximation in such models. The simplifying assumptions and approximations underlying these approaches will be reviewed and discussed in this contribution. The accuracy of some lumped-parameter model will be analyzed in order to show under which circumstances the approximate solutions can be satisfactorily employed. In particular, the focus will be on the comparison of the predictions that approximate and accurate methods provide when studying the influence of layer order and distribution on the thermal performance of multilayer structures.
Castet, Jean-Francois; Saleh, Joseph H.
2013-01-01
This article develops a novel approach and algorithmic tools for the modeling and survivability analysis of networks with heterogeneous nodes, and examines their application to space-based networks. Space-based networks (SBNs) allow the sharing of spacecraft on-orbit resources, such as data storage, processing, and downlink. Each spacecraft in the network can have different subsystem composition and functionality, thus resulting in node heterogeneity. Most traditional survivability analyses of networks assume node homogeneity and as a result, are not suited for the analysis of SBNs. This work proposes that heterogeneous networks can be modeled as interdependent multi-layer networks, which enables their survivability analysis. The multi-layer aspect captures the breakdown of the network according to common functionalities across the different nodes, and it allows the emergence of homogeneous sub-networks, while the interdependency aspect constrains the network to capture the physical characteristics of each node. Definitions of primitives of failure propagation are devised. Formal characterization of interdependent multi-layer networks, as well as algorithmic tools for the analysis of failure propagation across the network are developed and illustrated with space applications. The SBN applications considered consist of several networked spacecraft that can tap into each other's Command and Data Handling subsystem, in case of failure of its own, including the Telemetry, Tracking and Command, the Control Processor, and the Data Handling sub-subsystems. Various design insights are derived and discussed, and the capability to perform trade-space analysis with the proposed approach for various network characteristics is indicated. The select results here shown quantify the incremental survivability gains (with respect to a particular class of threats) of the SBN over the traditional monolith spacecraft. Failure of the connectivity between nodes is also examined, and the
Fundamental studies of interfacial rheology at multilayered model polymers for coextrusion process
NASA Astrophysics Data System (ADS)
Zhang, Huagui; Lamnawar, Khalid; Maazouz, Abderrahim
2015-05-01
Fundamental studies have been devoted to the interfacial phenomena at multilayered systems based on two model compatible polymers of PVDF and PMMA with varying molar masses. Linear and nonlinear rheology are demonstrated to be sensitive to the presence of diffuse interphase triggered at polymer/polymer interface. Firstly, the interdiffusion kinetics as well as the interphase development have been investigated using SAOS measurements with results analyzed under Doi-Edwards theory. The PMMA/PVDF mixture, has been examined to own close component monomeric friction coefficients. Based on this physics, a new rheological model was developed to quantify the interdiffusion coefficients. Thereby, rheological and geometrical properties of the interphase have been quantified, as validated by SEM-EDX. Secondly, step strain, shear and uniaxial extension startup were carried out to investigate their sensitivity to the diffuse interphase. An original model was proposed for the stress relaxation of multilayer and that of the interphase. Entanglement lack and weak entanglement intensity at the interface/diffuse interphase make them to be subsequently readily to suffer from interfacial yielding under large deformations. Finally, the interphase development coupled to flow in coextrusion has been considered. Net result between negative effect of chain orientation and favorable effect of flow has been shown to broaden the interphase. Its presence during coextrusion process was demonstrated to significantly weaken the interfacial instabilities.
NASA Astrophysics Data System (ADS)
Ferroukhi, M. Y.; Abahri, K.; Belarbi, R.; Limam, K.; Nouviaire, A.
2015-12-01
The present paper lies to study the coupled heat, air and moisture transfer in multi-layer building materials. Concerning the modeling part, the interest is to predict the hygrothermal behavior, by developing a macroscopic model that incorporates simultaneously the diffusive, convective and conductive effects on the building elements. Heat transfer is considered in the strongly coupled situation where the mass and heat flux are temperature, vapor pressure and total pressure dependents. The model input parameters are evaluated experimentally through the development of various experimental prototypes in the laboratory. Thereafter, an experimental setup has been established in order to evaluate the hygrothermal process of several multilayer walls configurations. The experimental procedure consists to follow the temperature and relative humidity evolutions within the samples thickness, submitted to controlled and fixed boundary conditions. This procedure points out diverging conclusion between different testing materials combinations (e.g. red-brick and polystyrene). In fact, the hygrothermal behavior of the tested configurations is completely dependent on both materials selection and their thermophysical properties. Finally, comparison between numerical and experimental results showed good agreement with acceptable errors margins with an average of 3 %.
Modeling Dental Health Care Workers' Risk of Occupational Infection from Bloodborne Pathogens.
ERIC Educational Resources Information Center
Capilouto, Eli; And Others
1990-01-01
The brief paper offers a model which permits quantification of the dental health care workers' risk of occupationally acquiring infection from bloodborne pathogens such as human immunodeficiency virus and hepatitis B virus. The model incorporates five parameters such as the probability that any individual patient is infected and number of patients…
NASA Astrophysics Data System (ADS)
Ponce de Leon, Lorenzo Angel
1992-09-01
A theory of the circular loop antenna constructed from finite conductivity wire is developed via a Fourier series expansion of the currents in the loop. Models for a family of small loop antennas are also presented. A new high sensitivity and selectivity heterodyne fiber optic based electromagnetic field detector is developed compatible with open antenna range measurements made at low signal levels and in the presence of strong interfering signals. A new analytical solution pertaining to the response of a disk loaded dipole antenna representing a dipole configured on a lossy dielectric medium is developed using a field compensation theorem and a geometrical theory of diffraction. The multipole expansions for the scattered fields of a multilayered infinite cylinder illuminated by oblique incidence plane wave are formulated and programmed for numerical analysis. The response of cylinders with constitutive parameters reflecting those used in human phantoms are calculated. The response of a small antenna proximal to a multilayered cylinder is analyzed. The scattered fields from multilayered bodies are coupled to a small wire antenna using a combined methods induced electromagnetic force (EMF) technique. New results concerning the response of a loop antenna near a multilayered body obtained via a zero and first phase current model are presented. The new technique is applied in the analysis of human phantoms tested in an open field antenna range. Validation of the theory of multilayered human phantoms with measurements using the new detector is demonstrated.
Assessment of coastal management options by means of multilayered ecosystem models
NASA Astrophysics Data System (ADS)
Nobre, Ana M.; Ferreira, João G.; Nunes, João P.; Yan, Xiaojun; Bricker, Suzanne; Corner, Richard; Groom, Steve; Gu, Haifeng; Hawkins, Anthony J. S.; Hutson, Rory; Lan, Dongzhao; Silva, João D. Lencart e.; Pascoe, Philip; Telfer, Trevor; Zhang, Xuelei; Zhu, Mingyuan
2010-03-01
This paper presents a multilayered ecosystem modelling approach that combines the simulation of the biogeochemistry of a coastal ecosystem with the simulation of the main forcing functions, such as catchment loading and aquaculture activities. This approach was developed as a tool for sustainable management of coastal ecosystems. A key feature is to simulate management scenarios that account for changes in multiple uses and enable assessment of cumulative impacts of coastal activities. The model was applied to a coastal zone in China with large aquaculture production and multiple catchment uses, and where management efforts to improve water quality are under way. Development scenarios designed in conjunction with local managers and aquaculture producers include the reduction of fish cages and treatment of wastewater. Despite the reduction in nutrient loading simulated in three different scenarios, inorganic nutrient concentrations in the bay were predicted to exceed the thresholds for poor quality defined by Chinese seawater quality legislation. For all scenarios there is still a Moderate High to High nutrient loading from the catchment, so further reductions might be enacted, together with additional decreases in fish cage culture. The model predicts that overall, shellfish production decreases by 10%-28% using any of these development scenarios, principally because shellfish growth is being sustained by the substances to be reduced for improvement of water quality. The model outcomes indicate that this may be counteracted by zoning of shellfish aquaculture at the ecosystem level in order to optimize trade-offs between productivity and environmental effects. The present case study exemplifies the value of multilayered ecosystem modelling as a tool for Integrated Coastal Zone Management and for the adoption of ecosystem approaches for marine resource management. This modelling approach can be applied worldwide, and may be particularly useful for the application of
Ma, Songyun; Scheider, Ingo; Bargmann, Swantje
2016-09-01
An anisotropic constitutive model is proposed in the framework of finite deformation to capture several damage mechanisms occurring in the microstructure of dental enamel, a hierarchical bio-composite. It provides the basis for a homogenization approach for an efficient multiscale (in this case: multiple hierarchy levels) investigation of the deformation and damage behavior. The influence of tension-compression asymmetry and fiber-matrix interaction on the nonlinear deformation behavior of dental enamel is studied by 3D micromechanical simulations under different loading conditions and fiber lengths. The complex deformation behavior and the characteristics and interaction of three damage mechanisms in the damage process of enamel are well captured. The proposed constitutive model incorporating anisotropic damage is applied to the first hierarchical level of dental enamel and validated by experimental results. The effect of the fiber orientation on the damage behavior and compressive strength is studied by comparing micro-pillar experiments of dental enamel at the first hierarchical level in multiple directions of fiber orientation. A very good agreement between computational and experimental results is found for the damage evolution process of dental enamel. PMID:27294283
NASA Technical Reports Server (NTRS)
Saylor, Rick D.; Wolfe, Glenn M.; Meyers, Tilden P.; Hicks, Bruce B.
2014-01-01
The Multilayer Model (MLM) has been used for many years to infer dry deposition fluxes from measured trace species concentrations and standard meteorological measurements for national networks in the U.S., including the U.S. Environmental Protection Agency's Clean Air Status and Trends Network (CASTNet). MLM utilizes a resistance analogy to calculate deposition velocities appropriate for whole vegetative canopies, while employing a multilayer integration to account for vertically varying meteorology, canopy morphology and radiative transfer within the canopy. However, the MLM formulation, as it was originally presented and as it has been subsequently employed, contains a non-physical representation related to the leaf-level quasi-laminar boundary layer resistance that affects the calculation of the total canopy resistance. In this note, the non-physical representation of the canopy resistance as originally formulated in MLM is discussed and a revised, physically consistent, formulation is suggested as a replacement. The revised canopy resistance formulation reduces estimates of HNO3 deposition velocities by as much as 38% during mid-day as compared to values generated by the original formulation. Inferred deposition velocities for SO2 and O3 are not significantly altered by the change in formulation (less than 3%). Inferred deposition loadings of oxidized and total nitrogen from CASTNet data may be reduced by 10-20% and 5-10%, respectively, for the Eastern U. S. when employing the revised formulation of MLM as compared to the original formulation.
The Integration of Ecological processes into a Multi-layer Higher order closure Land Surface Model
NASA Astrophysics Data System (ADS)
Chang, K. Y.; Paw U, K. T.; Chen, S. H.
2015-12-01
The ecological impacts on biogeophysical and biogeochemical processes were investigated by a series of simulations conducted by a multi-layer higher order closure land surface model (UCD-ACASA) driven by a variety of meteorological and ecological conditions. The results show that the implementation of a more realistic ecological dataset, once carefully quality controlled, can significantly improve the biogeophysical and biogeochemical simulations, which suggests that the ecological impacts on surface layer simulations are as important as the reliability of the selected land surface model. Therefore, the ability to simulate realistic ecological conditions is imperative and beneficial to improve weather and climate simulations. We coupled the ecological processes in UCD-ACASA by adapting the fully prognostic plant carbon and nitrogen dynamics from the version 4.5 of the Community Land Model (CLM4.5). The simulated ecological conditions are sensitive to both radiative transfer processes and leaf distribution inside the canopy, and the multi-layer feature built in UCD-ACASA enables it to describe these properties more realistically as compared to the other big-leaf models. We conducted another set of simulations to examine the reliability of the simulated biogeophysical, biogeochemical and ecological results. The simulated Leaf Area Index (LAI) was compared with a high resolution remotely sensed LAI dataset, and the results show that the simulated LAI tends to overestimate mean LAI and underestimate annual LAI variation at the selected sites. However, the simulated LAI is reasonable enough to produce comparable simulation results against the simulations driven directly by remotely sensed LAI for the tested biogeophysical and biogeochemical fluxes. The results show that ecological impacts on biogeophysical and biogeochemical simulations are significant, and the implementation of biogeochemical processes into a land surface model has the potential to improve weather and
Tyre/road interaction noise—A 3D viscoelastic multilayer model of a tyre belt
NASA Astrophysics Data System (ADS)
O'Boy, D. J.; Dowling, A. P.
2009-05-01
Vehicle noise is an increasing local environmental problem. For cars, above a steady speed of 40 km/h the noise produced by the interaction of the tyres with the road surface is the dominant noise source. In order to be able to predict this noise, the vibration characteristics of a stationary tyre must be determined. A multilayer viscoelastic cylindrical representation of the tyre belt, located between the sidewalls of the tyre and excluding the tread, is provided which yields the displacement and velocity response of the tyre belt when excited in the radial or tangential directions for a wide range of excitation frequencies, using only data from the design process. This model includes a representation of an air cavity and sidewalls and the response of the tyre belt is determined in both the frequency-wavenumber and time-spatial domains. The model can then be used to determine the noise of a tyre rolling on a rough road.
A generalized voter model with time-decaying memory on a multilayer network
NASA Astrophysics Data System (ADS)
Zhong, Li-Xin; Xu, Wen-Juan; Chen, Rong-Da; Zhong, Chen-Yang; Qiu, Tian; Shi, Yong-Dong; Wang, Li-Liang
2016-09-01
By incorporating a multilayer network and time-decaying memory into the original voter model, we investigate the coupled effects of spatial and temporal accumulation of peer pressure on the consensus. Heterogeneity in peer pressure and the time-decaying mechanism are both shown to be detrimental to the consensus. We find the transition points below which a consensus can always be reached and above which two opposed opinions are more likely to coexist. Our mean-field analysis indicates that the phase transitions in the present model are governed by the cumulative influence of peer pressure and the updating threshold. We find a functional relation between the consensus threshold and the decay rate of the influence of peer is found. As to the pressure. The time required to reach a consensus is governed by the coupling of the memory length and the decay rate. An intermediate decay rate may greatly reduce the time required to reach a consensus.
A multilayer model of time dependent deformation following an earthquake on a strike-slip fault
NASA Technical Reports Server (NTRS)
Cohen, S. C.
1981-01-01
A multilayer model of the Earth to calculate finite element of time dependent deformation and stress following an earthquake on a strike slip fault is discussed. The model involves shear properties of an elastic upper lithosphere, a standard viscoelastic linear solid lower lithosphere, a Maxwell viscoelastic asthenosphere and an elastic mesosphere. Systematic variations of fault and layer depths and comparisons with simpler elastic lithosphere over viscoelastic asthenosphere calculations are analyzed. Both the creep of the lower lithosphere and astenosphere contribute to the postseismic deformation. The magnitude of the deformation is enhanced by a short distance between the bottom of the fault (slip zone) and the top of the creep region but is less sensitive to the thickness of the creeping layer. Postseismic restressing is increased as the lower lithosphere becomes more viscoelastic, but the tendency for the width of the restressed zone to growth with time is retarded.
NASA Astrophysics Data System (ADS)
Gong, Xuepeng; Lu, Qipeng; Lu, Guoqing
2015-02-01
Carbon contamination on extreme ultraviolet (EUV) multi-layer mirror is a seriously restrictive factor for lithography quality, chip output and life of lithography machine. In order to estimate the carbon contamination of EUV multi-layer and study the mechanism of carbon contamination deeply, an effective theoretical model of the carbon deposition on the multi-layer surface and experimental equipment for studying the carbon contamination are established. The theoretical model describes the transport of residual hydrocarbons to the irradiated area and the subsequent dissociation of the hydrocarbon by direct EUV radiation and secondary electron excitation, and indicates that the direct EUV radiation is the primary reason to dissociate the hydrocarbon, and makes the carbon deposited on the surface of multi-layer. Various carbon deposition states are simulated by the theoretical model, and some effective simulated results are obtained. Optical design scheme and structure design scheme of the experimental equipment are presented. The optical system includes two spherical multi-layer mirrors and a plane mirror multi-layer mirror. Ray trace and EUV intensity on sample are calculated, the light spot on sample is about Φ10mm and the EUV intensity is about 0.126mW/mm2. Structure of the experimental equipment includes adjusting mechanism of two spherical mirrors, rotary mechanism of plane mirror, alignment mechanism of EUV source, adjusting mechanism of sample, and so on. After testing, linear resolution and angle resolution of two spherical mirrors adjusting mechanism are 1μm and 5μrad respectively; linear displacement and linear resolution of sample adjusting mechanism are 50mm and 1μm respectively. The structure design scheme meets the requirement of the carbon contamination experiment.
Single-element modeling of multilayer constrained-layer damping treatments
NASA Astrophysics Data System (ADS)
Agnes, Gregory S.
1995-05-01
The use of multi-layer constrained layer damping treatments on plate-like structures provides broadband vibration damping over a wide temperature range. A difficulty with the design of such treatments is their modeling. The current state of the art requires a separate plate element for each constraining layer plus a solid element for each viscoelastic layer in the thickness direction. The number of degrees of freedom is large conflicting with the iterative approach necessitated by the frequency and temperature dependance of the material properties which dictates that a small model size must be maintained. The large model size also slows optimization. The goal of this research was to produce a true plate finite element model which uses only a few degrees of freedom per node. This model is obtained by using a variational asymptotical theory to correctly capture the layerwise jumps in the stress and strain fields. A model is developed for simply supported plates which can later be extended to a more general finite element. Results are compared with the exact elasticity solution of Pagano. They show an excellent match exists in the predicted stress and strain field. The model is also compared with RKU analysis for plates again demonstrating its accuracy. A future finite element model based on this theory would require only six extra degrees of freedom per node with only one element in the thickness direction, thus simplifying the modeling of constrained layer damping treatments.
Pigozzi, Giancarlo; Janczak-Rusch, Jolanta; Passerone, Daniele; Antonio Pignedoli, Carlo; Patscheider, Joerg; Jeurgens, Lars P. H.; Antusek, Andrej; Parlinska-Wojtan, Magdalena; Bissig, Vinzenz
2012-10-29
Nano-sized Ag-Cu{sub 8nm}/AlN{sub 10nm} multilayers were deposited by reactive DC sputtering on {alpha}-Al{sub 2}O{sub 3}(0001) substrates. Investigation of the phase constitution and interface structure of the multilayers evidences a phase separation of the alloy sublayers into nanosized grains of Ag and Cu. The interfaces between the Ag grains and the quasi-single-crystalline AlN sublayers are semi-coherent, whereas the corresponding Cu/AlN interfaces are incoherent. The orientation relationship between Ag and AlN is constant throughout the entire multilayer stack. These observations are consistent with atomistic models of the interfaces as obtained by ab initio calculations.
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In-to-Out Body Antenna-Independent Path Loss Model for Multilayered Tissues and Heterogeneous Medium
Kurup, Divya; Vermeeren, Günter; Tanghe, Emmeric; Joseph, Wout; Martens, Luc
2015-01-01
In this paper, we investigate multilayered lossy and heterogeneous media for wireless body area networks (WBAN) to develop a simple, fast and efficient analytical in-to-out body path loss (PL) model at 2.45 GHz and, thus, avoid time-consuming simulations. The PL model is an antenna-independent model and is validated with simulations in layered medium, as well as in a 3D human model using electromagnetic solvers. PMID:25551483
Kurup, Divya; Vermeeren, Günter; Tanghe, Emmeric; Joseph, Wout; Martens, Luc
2015-01-01
In this paper, we investigate multilayered lossy and heterogeneous media for wireless body area networks (WBAN) to develop a simple, fast and efficient analytical in-to-out body path loss (PL) model at 2.45 GHz and, thus, avoid time-consuming simulations. The PL model is an antenna-independent model and is validated with simulations in layered medium, as well as in a 3D human model using electromagnetic solvers. PMID:25551483
An Articulation Model in Dental Assisting for the Commonwealth of Pennsylvania. A Continuation.
ERIC Educational Resources Information Center
Sylves, Jane M.; Boody, Sandra
A curriculum development project was conducted to generate additional competency-based modules to be used within the articulation model for Pennsylvania dental assisting programs, established in 1988. Project activities included reviewing, modifying, and providing parallel competency-based structure for the courses at the A.W. Beattie Technical…
NASA Technical Reports Server (NTRS)
Chou, M.-D.; Arking, A.; Peng, L.
1984-01-01
A multilayer energy balance model is applied in an examination of the sensitivity of climate to stratospheric aerosols induced by volcanic eruptions. Zonally and annually averaged quantities are considered, with ocean and land temperatures computed separately and the atmosphere below the 200 mb level divided into eight layers of 24 sublayers each. The aerosol is assumed to form in the 150-200 mb range. Aerosol parameters for radiative transfer calculations are reflection in the solar spectral region and absorption in the solar and IR regions. A 75 percent aqueous solution of sulfuric acid is assumed for the aerosols. The sensitivity of the hemispherically averaged surface temperature is enhanced 37 percent, with a 20 percent uncertainty, when the thermal IR radiation is excluded. The solar radiation enhances the surface temperatures to a higher degree than the thermal radiation. The maximum response to the evenly distributed aerosols is in the 60-70 deg N latitudes and propagates, weakening, to lower latitudes.
A multilayer evaluation approach for protein structure prediction and model quality assessment.
Zhang, Jingfen; Wang, Qingguo; Vantasin, Kittinun; Zhang, Jiong; He, Zhiquan; Kosztin, Ioan; Shang, Yi; Xu, Dong
2011-01-01
Protein tertiary structures are essential for studying functions of proteins at molecular level. An indispensable approach for protein structure solution is computational prediction. Most protein structure prediction methods generate candidate models first and select the best candidates by model quality assessment (QA). In many cases, good models can be produced, but the QA tools fail to select the best ones from the candidate model pool. Because of incomplete understanding of protein folding, each QA method only reflects partial facets of a structure model and thus has limited discerning power with no one consistently outperforming others. In this article, we developed a set of new QA methods, including two QA methods for evaluating target/template alignments, a molecular dynamics (MD)-based QA method, and three consensus QA methods with selected references to reveal new facets of protein structures complementary to the existing methods. Moreover, the underlying relationship among different QA methods were analyzed and then integrated into a multilayer evaluation approach to guide the model generation and model selection in prediction. All methods are integrated and implemented into an innovative and improved prediction system hereafter referred to as MUFOLD. In CASP8 and CASP9, MUFOLD has demonstrated the proof of the principles in terms of both QA discerning power and structure prediction accuracy. PMID:21997706
NASA Astrophysics Data System (ADS)
Hawley, M. E.; Devlin, D. J.; Reichhardt, C. J.; Sickafus, K. E.; Usov, I. O.; Valdez, J. A.; Wang, Y. Q.
2010-10-01
This work explored a potential new model dispersion fuel form consisting of an actinide material embedded in a radiation tolerant matrix that captures fission products (FPs) and is easily separated chemically as waste from the fuel material. To understand the stability of this proposed dispersion fuel form design, an idealized model system composed of a multilayer film was studied. This system consisted of a tri-layer structure of an MgO layer sandwiched between two HfO 2 layers. HfO 2 served as a surrogate fissile material for UO 2 while MgO represented a stable, fissile product (FP) getter that is easily separated from the fissile material. This type of multilayer film structure allowed us to control the size of and spacing between each layer. The films were grown at room temperature by e-beam deposition on a Si(1 1 1) substrate and post-annealed annealing at a range of temperatures to crystallize the HfO 2 layers. The 550 °C annealed sample was subsequently irradiated with 10 MeV Au 3+ ions at a range of fluences from 5 × 10 13 to 3.74 × 10 16 ions/cm 2. Separate single layer constituent films and the substrate were also irradiated at 5 × 10 15 and 8 × 10 14 and 2 × 10 16, respectively. After annealing and irradiation, the samples were characterized using atomic force imaging techniques to determine local changes in microstructure and mechanical properties. All samples annealed above 550 °C cracked. From the AFM results we observed both crack healing and significant modification of the surface at higher fluences.
A multilayer model for inferring dry deposition using standard meteorological measurements
NASA Astrophysics Data System (ADS)
Meyers, Tilden P.; Finkelstein, Peter; Clarke, John; Ellestad, Thomas G.; Sims, Pamela F.
1998-09-01
In this paper, we describe the latest version of the dry deposition inferential model, which is used to estimate the deposition velocities (Vd) for SO2, O3, HNO3, and particles with diameters less than 2 μm. The dry deposition networks operated by the National Oceanic and Atmospheric Administration (NOAA) and the Environmental Protection Agency (EPA) use this model to estimate dry deposition on a weekly basis. This model uses a multilayer approach, discretizing the vegetated canopy into 20 layers. The use of canopy radiative transfer and simple wind profile models allows for estimates of stomatal (rs) and leaf boundary layer (rb) resistances to be determined at each layer in the plant canopy for both sunlit and shaded leaves. The effect of temperature, water stress, and vapor pressure deficits on the stomatal resistance (rs) have been included. Comparisons of modeled deposition velocities are made with extensive direct measurements performed at three different locations with different crops. The field experiment is discussed in some detail. Overall, modeled O3 deposition velocities are in good agreement with measured values with the average mean bias for all surfaces of the order of 0.01 cm/s or less. For SO2, mean biases range from -0.05 for corn to 0.15 cm/s for soybeans, while for HNO3, they range from 0.09 for corn to 0.47 cm/s for pasture.
NASA Astrophysics Data System (ADS)
Ryder, J.; Polcher, J.; Peylin, P.; Ottlé, C.; Chen, Y.; van Gorsel, E.; Haverd, V.; McGrath, M. J.; Naudts, K.; Otto, J.; Valade, A.; Luyssaert, S.
2016-01-01
In Earth system modelling, a description of the energy budget of the vegetated surface layer is fundamental as it determines the meteorological conditions in the planetary boundary layer and as such contributes to the atmospheric conditions and its circulation. The energy budget in most Earth system models has been based on a big-leaf approach, with averaging schemes that represent in-canopy processes. Furthermore, to be stable, that is to say, over large time steps and without large iterations, a surface layer model should be capable of implicit coupling to the atmospheric model. Surface models with large time steps, however, have difficulties in reproducing consistently the energy balance in field observations. Here we outline a newly developed numerical model for energy budget simulation, as a component of the land surface model ORCHIDEE-CAN (Organising Carbon and Hydrology In Dynamic Ecosystems - CANopy). This new model implements techniques from single-site canopy models in a practical way. It includes representation of in-canopy transport, a multi-layer long-wave radiation budget, height-specific calculation of aerodynamic and stomatal conductance, and interaction with the bare-soil flux within the canopy space. Significantly, it avoids iterations over the height of the canopy and so maintains implicit coupling to the atmospheric model LMDz (Laboratoire de Météorologie Dynamique Zoomed model). As a first test, the model is evaluated against data from both an intensive measurement campaign and longer-term eddy-covariance measurements for the intensively studied Eucalyptus stand at Tumbarumba, Australia. The model performs well in replicating both diurnal and annual cycles of energy and water fluxes, as well as the vertical gradients of temperature and of sensible heat fluxes.
Analytical modeling and optimization of DEAP-based multilayer stack-transducers
NASA Astrophysics Data System (ADS)
Hoffstadt, Thorben; Maas, Jürgen
2015-09-01
Transducers based on dielectric electroactive polymers (DEAP) use electrostatic pressure to convert electrical into mechanical energy or vice versa. To scale up the actuation or the energy gain, multilayer transducers like DEAP stack transducers are appropriate. Within this contribution, a model of such a stack transducer is derived and experimentally validated. The model is based on a multi-domain approach to describe the mechanical dynamics and the electrical behavior of the DEAP. Since these two domains influence each other they are coupled afterwards by a novel approach using interchanging power flows. To parametrize this model, tensile and compression tests for different polymer materials were performed under static and transient considerations. The results of these experiments show that the parameters obtained from the tensile test sufficiently describe the compression mode and can therefore be used for the model. Based on this transducer model the overall energy and the different parts of the multi-domain are analytically determined for arbitrary operating points. These expressions for the energies are finally used to optimize well-defined coupling coefficients, by which a maximum part of the electrical input energy is converted to mechanical energy, especially mechanical work.
Analytical Models for Variable Density Multilayer Insulation Used in Cryogenic Storage
NASA Technical Reports Server (NTRS)
Hedayat, A.; Hastings, L. J.; Brown, T.
2001-01-01
A unique multilayer insulation concept for orbital cryogenic storage was experimentally evaluated at NASA Marshall Space Flight Center (MSFC) using the Multipurpose Hydrogen Test Bed (MHTB). A combination of foam/Multi layer Insulation (MLI) was used. The MLI (45 layers of Double Aluminized Mylar (DAM) with Dacron net spacers) was designed for an on-orbit storage period of 45 days and included several unique features such as: a variable layer density and larger but fewer DAM perforations for venting during ascent to orbit. The focus of this paper is on analytical modeling of the variable density MLI performance during orbital coast periods. The foam/MLI combination model is considered to have five segments. The first segment represents the foam layer. The second, third, and fourth segments represent the three layers of MLI with different layer densities and number of shields. Finally, the last segment is considered to be a shroud that surrounds the last MLI layer. The hot boundary temperature is allowed to vary from 164 K to 305 K. To simulate MLI performance, two approaches are considered. In the first approach, the variable density MLI is modeled layer by layer while in the second approach, a semi-empirical model is applied. Both models account for thermal radiation between shields, gas conduction, and solid conduction through the separator materials. The heat flux values predicted by each approach are compared for different boundary temperatures and MLI systems with 30, 45, 60, and 75 layers.
NASA Technical Reports Server (NTRS)
Hastings, L. J.; Hedayat, A.; Brown, T. M.
2004-01-01
A unique foam/multilayer insulation (MLI) combination concept for orbital cryogenic storage was experimentally evaluated using a large-scale hydrogen tank. The foam substrate insulates for ground-hold periods and enables a gaseous nitrogen purge as opposed to helium. The MLI, designed for an on-orbit storage period for 45 days, includes several unique features including a variable layer density and larger but fewer perforations for venting during ascent to orbit. Test results with liquid hydrogen indicated that the MLI weight or tank heat leak is reduced by about half in comparison with standard MLI. The focus of this effort is on analytical modeling of the variable density MLI (VD-MLI) on-orbit performance. The foam/VD-MLI model is considered to have five segments. The first segment represents the optional foam layer. The second, third, and fourth segments represent three different MLI layer densities. The last segment is an environmental boundary or shroud that surrounds the last MLI layer. Two approaches are considered: a variable density MLI modeled layer by layer and a semiempirical model or "modified Lockheed equation." Results from the two models were very comparable and were within 5-8 percent of the measured data at the 300 K boundary condition.
NASA Astrophysics Data System (ADS)
Tefft, Edward C.; Anton, Steven R.
2016-04-01
As electronic devices become both ubiquitous and more energy efficient, powering them with energy harvested from, for example, piezoelectric materials has become a subject of much interest. The field does indeed show promise, as harvesting energy from smart materials has the potential to replace batteries completely in some low-power applications. This paper presents modeling of piezo-electret foam assembled in a multilayer stack configuration, with the required adhesives and conductors, as a multiple degree of freedom (MDOF) system. The benefits of using the foam over some piezo-ceramics include its high flexibility, its light weight, and its lead-free composition. This model predicts the mechanical and electromechanical response to base excitation for any number of layers of piezo-electret foam. Building upon previous work which modeled the piezo-electret stack as a single degree of freedom (SDOF) system, the MDOF model provides information concerning the response of internal stack layers. The MDOF model is validated against the experimentally determined mechanical and electrical responses of a 20-layer piezo-electret foam stack. Also, the internal stack dynamics at higher order vibration modes suggest that charge cancellation is a serious outcome of vibration at these modes that designers need to consider.
NASA Astrophysics Data System (ADS)
Altunkaynak, Abdüsselam; Strom, Kyle B.
2009-12-01
This study uses multilayer perceptron (MP) methods to develop classification models for predicting cascade, step-pool, plane bed, and pool-riffle type reach morphologies in mountain streams. Several models were developed with MP and classical linear regression methods on the basis of the following input variables: channel slope (S), sediment size (d84), bankfull depth (h), and bankfull width (w). Data for model calibration and testing were compiled from previous studies in mountain environments. The data were divided into separate calibration (training) and testing (prediction) sets for both the MP and classical linear regression methods; model performance was based on the percentage of accurately predicted reach morphologies using the testing portion of the data. The results indicate that (1) the MP models outperformed the linear regression models for reach morphology classification; (2) relative submergence (h/d84) was useful for classifying step-pool and pool-riffle reaches but performed poorly in discriminating cascade and plane bed type reaches; (3) inclusion of channel slope in models was important for classifying cascade type reaches; and (4) plane bed reaches were the most difficult to classify and delineate from pool-riffle reaches. The two best performing MP models included the input variables (S, h/d84) and (S, h/d84, w). The overall predictive accuracy for classification of reach type for the two models was 81% and 83%, respectively, with predictive accuracies by reach type as follows: cascade, 100%; step-pool, 81%; plane bed, 67%; pool-riffle, 88% (first model) and cascade, 100%; step-pool, 87%; plane bed, 70%; pool-riffle, 90% (second model).
NASA Astrophysics Data System (ADS)
Ryder, J.; Polcher, J.; Peylin, P.; Ottlé, C.; Chen, Y.; van Gorsel, E.; Haverd, V.; McGrath, M. J.; Naudts, K.; Otto, J.; Valade, A.; Luyssaert, S.
2014-12-01
In Earth system modelling, a description of the energy budget of the vegetated surface layer is fundamental as it determines the meteorological conditions in the planetary boundary layer and as such contributes to the atmospheric conditions and its circulation. The energy budget in most Earth system models has long been based on a "big-leaf approach", with averaging schemes that represent in-canopy processes. Such models have difficulties in reproducing consistently the energy balance in field observations. We here outline a newly developed numerical model for energy budget simulation, as a component of the land surface model ORCHIDEE-CAN (Organising Carbon and Hydrology In Dynamic Ecosystems - CANopy). This new model implements techniques from single-site canopy models in a practical way. It includes representation of in-canopy transport, a multilayer longwave radiation budget, height-specific calculation of aerodynamic and stomatal conductance, and interaction with the bare soil flux within the canopy space. Significantly, it avoids iterations over the height of tha canopy and so maintains implicit coupling to the atmospheric model LMDz. As a first test, the model is evaluated against data from both an intensive measurement campaign and longer term eddy covariance measurements for the intensively studied Eucalyptus stand at Tumbarumba, Australia. The model performs well in replicating both diurnal and annual cycles of fluxes, as well as the gradients of sensible heat fluxes. However, the model overestimates sensible heat flux against an underestimate of the radiation budget. Improved performance is expected through the implementation of a more detailed calculation of stand albedo and a more up-to-date stomatal conductance calculation.
Dispersion and kinematics of multi-layer non-hydrostatic models
NASA Astrophysics Data System (ADS)
Bai, Yefei; Cheung, Kwok Fai
2015-08-01
Multi-layer non-hydrostatic models are gaining popularity in studies of coastal wave processes owing to the resolution of the flow kinematics, but the linear dispersion relation remains the primary criterion for assessment of model convergence. In this paper, we reformulate the linear governing equations of an N-layer model into Boussinesq form by writing the non-hydrostatic terms as high-order derivatives of the horizontal flow velocity. The equation structure allows implementation of Fourier analysis to provide a [2 N - 2, 2N] expansion of the velocity at each layer. A variable transformation converts the governing equations into separate flux- and dispersion-dominated systems, which explicitly give an equivalent Pade´ expansion of the wave celerity for examination of the convergence and asymptotic properties. Flow continuity equates the depth-integrated horizontal velocity to the celerity and verifies the analytical solution. The surface-layer velocity, which is driven by the kinematic free surface boundary condition, shows a positive error and converges monotonically to the solution of Airy wave theory. When the depth parameter kd > 2N, flow reversal occurs in the sub-surface layers to offset overestimation of the surface velocity and to better approximate the flux. This model internal mechanism facilitates convergence of the celerity at large kd and benefits applications on wave transformation. Such non-physical flow reversal, however, might complicate studies that require detailed wave kinematics.
A Multilayer Naïve Bayes Model for Analyzing User's Retweeting Sentiment Tendency
Wang, Mengmeng; Zuo, Wanli; Wang, Ying
2015-01-01
Today microblogging has increasingly become a means of information diffusion via user's retweeting behavior. Since retweeting content, as context information of microblogging, is an understanding of microblogging, hence, user's retweeting sentiment tendency analysis has gradually become a hot research topic. Targeted at online microblogging, a dynamic social network, we investigate how to exploit dynamic retweeting sentiment features in retweeting sentiment tendency analysis. On the basis of time series of user's network structure information and published text information, we first model dynamic retweeting sentiment features. Then we build Naïve Bayes models from profile-, relationship-, and emotion-based dimensions, respectively. Finally, we build a multilayer Naïve Bayes model based on multidimensional Naïve Bayes models to analyze user's retweeting sentiment tendency towards a microblog. Experiments on real-world dataset demonstrate the effectiveness of the proposed framework. Further experiments are conducted to understand the importance of dynamic retweeting sentiment features and temporal information in retweeting sentiment tendency analysis. What is more, we provide a new train of thought for retweeting sentiment tendency analysis in dynamic social networks. PMID:26417367
A Multilayer Naïve Bayes Model for Analyzing User's Retweeting Sentiment Tendency.
Wang, Mengmeng; Zuo, Wanli; Wang, Ying
2015-01-01
Today microblogging has increasingly become a means of information diffusion via user's retweeting behavior. Since retweeting content, as context information of microblogging, is an understanding of microblogging, hence, user's retweeting sentiment tendency analysis has gradually become a hot research topic. Targeted at online microblogging, a dynamic social network, we investigate how to exploit dynamic retweeting sentiment features in retweeting sentiment tendency analysis. On the basis of time series of user's network structure information and published text information, we first model dynamic retweeting sentiment features. Then we build Naïve Bayes models from profile-, relationship-, and emotion-based dimensions, respectively. Finally, we build a multilayer Naïve Bayes model based on multidimensional Naïve Bayes models to analyze user's retweeting sentiment tendency towards a microblog. Experiments on real-world dataset demonstrate the effectiveness of the proposed framework. Further experiments are conducted to understand the importance of dynamic retweeting sentiment features and temporal information in retweeting sentiment tendency analysis. What is more, we provide a new train of thought for retweeting sentiment tendency analysis in dynamic social networks. PMID:26417367
NASA Astrophysics Data System (ADS)
Chaudhuri, Sutapa; Das, Debanjana; Sarkar, Ishita; Goswami, Sayantika
2015-10-01
The reduction in the visibility during fog significantly influences surface as well as air transport operations. The prediction of fog remains difficult despite improvements in numerical weather prediction models. The present study aims at identifying a suitable neural network model with proper architecture to provide precise nowcast of the horizontal visibility during fog over the airports of three significantly affected metropolises of India, namely: Kolkata (22°32'N; 88°20'E), Delhi (28°38'N; 77°12'E) and Bengaluru (12°95'N; 77°72'E). The investigation shows that the multilayer perceptron (MLP) model provides considerably less error in nowcasting the visibility during fog over the said metropolises than radial basis function network, generalized regression neural network or linear neural network. The MLP models of different architectures are trained with the data and records from 2000 to 2010. The model results are validated with observations from 2011 to 2014. Our results reveal that MLP models with different configurations (1) four input layers, three hidden layers with three hidden nodes in each layer and a single output; (2) four input layers with two hidden layers having one hidden node in the first hidden layer and two hidden nodes in the second hidden layer, and a single output layer; and (3) four input layers with two hidden layers having two hidden nodes in each hidden layer and a single output layer] provide minimum error in nowcasting the visibility during fog over the airports of Kolkata, Delhi and Bengaluru, respectively. The results show that the MLP model is well suited for nowcasting visibility during fog with 6 h lead time, however, the study reveals that the MLP model sensitive to dissimilar station altitudes in nowcasting visibility, as the minimum prediction error for the three metropolises having dissimilar mean sea level altitudes is observed through different configurations of the model.
Analytic Element Modeling of Steady Interface Flow in Multilayer Aquifers Using AnAqSim.
Fitts, Charles R; Godwin, Joshua; Feiner, Kathleen; McLane, Charles; Mullendore, Seth
2015-01-01
This paper presents the analytic element modeling approach implemented in the software AnAqSim for simulating steady groundwater flow with a sharp fresh-salt interface in multilayer (three-dimensional) aquifer systems. Compared with numerical methods for variable-density interface modeling, this approach allows quick model construction and can yield useful guidance about the three-dimensional configuration of an interface even at a large scale. The approach employs subdomains and multiple layers as outlined by Fitts (2010) with the addition of discharge potentials for shallow interface flow (Strack 1989). The following simplifying assumptions are made: steady flow, a sharp interface between fresh- and salt water, static salt water, and no resistance to vertical flow and hydrostatic heads within each fresh water layer. A key component of this approach is a transition to a thin fixed minimum fresh water thickness mode when the fresh water thickness approaches zero. This allows the solution to converge and determine the steady interface position without a long transient simulation. The approach is checked against the widely used numerical codes SEAWAT and SWI/MODFLOW and a hypothetical application of the method to a coastal wellfield is presented. PMID:24942663
Irreducibility of multilayer network dynamics: the case of the voter model
NASA Astrophysics Data System (ADS)
Diakonova, Marina; Nicosia, Vincenzo; Latora, Vito; San Miguel, Maxi
2016-02-01
We address the issue of the reducibility of the dynamics on a multilayer network to an equivalent process on an aggregated single-layer network. As a typical example of models for opinion formation in social networks, we implement the voter model on a two-layer multiplex network, and we study its dynamics as a function of two control parameters, namely the fraction of edges simultaneously existing in both layers of the network (edge overlap), and the fraction of nodes participating in both layers (interlayer connectivity or degree of multiplexity). We compute the asymptotic value of the number of active links (interface density) in the thermodynamic limit, and the time to reach an absorbing state for finite systems, and we compare the numerical results with the analytical predictions on equivalent single-layer networks obtained through various possible aggregation procedures. We find a large region of parameters where the interface density of large multiplexes gives systematic deviations from that of the aggregates. We show that neither of the standard unweighted aggregation procedures is able to capture the highly nonlinear increase in the lifetime of a finite size multiplex at small interlayer connectivity. These results indicate that multiplexity should be appropriately taken into account when studying voter model dynamics, and that, in general, single-layer approximations might be not accurate enough to properly understand processes occurring on multiplex networks, since they might flatten out relevant dynamical details.
3-dimensional orthodontics visualization system with dental study models and orthopantomograms
NASA Astrophysics Data System (ADS)
Zhang, Hua; Ong, S. H.; Foong, K. W. C.; Dhar, T.
2005-04-01
The aim of this study is to develop a system that provides 3-dimensional visualization of orthodontic treatments. Dental plaster models and corresponding orthopantomogram (dental panoramic tomogram) are first digitized and fed into the system. A semi-auto segmentation technique is applied to the plaster models to detect the dental arches, tooth interstices and gum margins, which are used to extract individual crown models. 3-dimensional representation of roots, generated by deforming generic tooth models with orthopantomogram using radial basis functions, is attached to corresponding crowns to enable visualization of complete teeth. An optional algorithm to close the gaps between deformed roots and actual crowns by using multi-quadratic radial basis functions is also presented, which is capable of generating smooth mesh representation of complete 3-dimensional teeth. User interface is carefully designed to achieve a flexible system with as much user friendliness as possible. Manual calibration and correction is possible throughout the data processing steps to compensate occasional misbehaviors of automatic procedures. By allowing the users to move and re-arrange individual teeth (with their roots) on a full dentition, this orthodontic visualization system provides an easy and accurate way of simulation and planning of orthodontic treatment. Its capability of presenting 3-dimensional root information with only study models and orthopantomogram is especially useful for patients who do not undergo CT scanning, which is not a routine procedure in most orthodontic cases.
Synthetic, Multi-Layer, Self-Oscillating Vocal Fold Model Fabrication
Murray, Preston R.; Thomson, Scott L.
2011-01-01
, however, have either been homogenous (one-layer models) or have been fabricated using two materials of differing stiffness (two-layer models). This approach does not allow for representation of the actual multi-layer structure of the human vocal folds 1 that plays a central role in governing vocal fold flow-induced vibratory response. Consequently, one- and two-layer synthetic vocal fold models have exhibited disadvantages 3,6,8 such as higher onset pressures than what are typical for human phonation (onset pressure is the minimum lung pressure required to initiate vibration), unnaturally large inferior-superior motion, and lack of a "mucosal wave" (a vertically-traveling wave that is characteristic of healthy human vocal fold vibration). In this paper, fabrication of a model with multiple layers of differing material properties is described. The model layers simulate the multi-layer structure of the human vocal folds, including epithelium, superficial lamina propria (SLP), intermediate and deep lamina propria (i.e., ligament; a fiber is included for anterior-posterior stiffness), and muscle (i.e., body) layers 1. Results are included that show that the model exhibits improved vibratory characteristics over prior one- and two-layer synthetic models, including onset pressure closer to human onset pressure, reduced inferior-superior motion, and evidence of a mucosal wave. PMID:22157812
Synthetic, multi-layer, self-oscillating vocal fold model fabrication.
Murray, Preston R; Thomson, Scott L
2011-01-01
been homogenous (one-layer models) or have been fabricated using two materials of differing stiffness (two-layer models). This approach does not allow for representation of the actual multi-layer structure of the human vocal folds that plays a central role in governing vocal fold flow-induced vibratory response. Consequently, one- and two-layer synthetic vocal fold models have exhibited disadvantages such as higher onset pressures than what are typical for human phonation (onset pressure is the minimum lung pressure required to initiate vibration), unnaturally large inferior-superior motion, and lack of a "mucosal wave" (a vertically-traveling wave that is characteristic of healthy human vocal fold vibration). In this paper, fabrication of a model with multiple layers of differing material properties is described. The model layers simulate the multi-layer structure of the human vocal folds, including epithelium, superficial lamina propria (SLP), intermediate and deep lamina propria (i.e., ligament; a fiber is included for anterior-posterior stiffness), and muscle (i.e., body) layers. Results are included that show that the model exhibits improved vibratory characteristics over prior one- and two-layer synthetic models, including onset pressure closer to human onset pressure, reduced inferior-superior motion, and evidence of a mucosal wave. PMID:22157812
A Multi-layer Radiation Model for Urban Neighbourhoods with Trees
NASA Astrophysics Data System (ADS)
Krayenhoff, E. S.; Christen, A.; Martilli, A.; Oke, T. R.
2014-04-01
A neighbourhood-scale multi-layer urban canopy model of shortwave and longwave radiation exchange that explicitly includes the radiative effects of tall vegetation (trees) is presented. Tree foliage is permitted both between and above buildings, and mutual shading, emission and reflection between buildings and trees are included. The basic geometry is a two-dimensional canyon with leaf area density profiles and probabilistic variation of building height. Furthermore, the model accounts for three-dimensional path lengths through the foliage. Ray tracing determines the receipt of direct shortwave irradiance by building and foliage elements. View factors for longwave and shortwave diffuse radiation exchange are computed once at the start of the simulation using a Monte Carlo ray tracing approach; for subsequent model timesteps, matrix inversion rapidly solves infinite reflections and interception of emitted longwave between all elements. The model is designed to simulate any combination of shortwave and longwave radiation frequency bands, and to be portable to any neighbourhood-scale urban canopy geometry based on the urban canyon. Additionally, the model is sufficiently flexible to represent forest and forest-clearing scenarios. Model sensitivity tests demonstrate the model is robust and computationally feasible, and highlight the importance of vertical resolution to the performance of urban canopy radiation models. Full model evaluation is limited by the paucity of within-canyon radiation measurements in urban neighbourhoods with trees. Where appropriate model components are tested against analytic relations and results from an independent urban radiation transfer model. Furthermore, system response tests demonstrate the ability of the model to realistically distribute shortwave radiation among urban elements as a function of built form, solar angle and tree foliage height, density and clumping. Separate modelling of photosynthetically-active and near
Chawla, O; Atack, N E; Deacon, S A; Leary, S D; Ireland, A J; Sandy, J R
2013-03-01
Objective : To determine the reliability and reproducibility of using three-dimensional digital models as an alternative to plaster models for rating dental arch relationships in patients born with unilateral cleft lip and palate. Design : Reliability and reproducibility study. Methods : Study models of 45 patients born with unilateral cleft lip and palate were made available in plaster and three-dimensional digital models. Records were scored a week apart by three examiners using the 5-year-olds' index reference models in the same two formats as the patient models. To assess reproducibility the study was repeated 4 weeks later under similar conditions to minimize the influence of memory bias on the results. The reliability of using the three-dimensional digital models was determined by comparing the scores for each examiner with the plaster model scores. Results : Weighted kappa statistics indicated repeatability for the plaster models was very good (.83 to .87). For the three-dimensional digital models it was good to very good (.74 to .83). Overall, the use of the three-dimensional digital models showed good agreement with the plaster model scores on both occasions. Conclusion : Three-dimensional digital models appear to be a good alternative to plaster models for assessing dental arch relationships using the 5-year-olds' index. PMID:22420605
A model describing the microwave emission from a multi-layer snowpack at 37 GHz
NASA Technical Reports Server (NTRS)
Abdelrazik, M.; Ulaby, F.; Stiles, H.
1981-01-01
A multilayer emission model is described and applied to emission measurements obtained at 37 GHz and H polarization using a microwave radiometer attached to a truck-mounted boom in Steamboat Springs, Colorado in 1977. Estimated absorption and scattering coefficients and their dependence on wetness were obtained using calculated values of the dielectric constant at 37 GHz along with the model. It was found that the scattering coefficient is comparable in value to the absorption coefficient for dry snow however, the absorption coefficient increases linearly with increasing snow wetness while the scattering coefficient decreases linearly with increasing wetness. The emission from each layer of the snowpack was also calculated using the estimated coefficients. It is shown that for dry snow, the ground underneath the snowpack contributes about 45% of all measured emission while the rest is due to emission from all the layers within the snowpack. When the wetness of the top 5 cm layer of snowpack increases to about 2% by volume, this top 5 cm snowlayer contributes more than 90% of all the measured emission.
Examining the impact of multi-layer graphene using cellular and amphibian models
NASA Astrophysics Data System (ADS)
Muzi, Laura; Mouchet, Florence; Cadarsi, Stéphanie; Janowska, Izabela; Russier, Julie; Ménard-Moyon, Cécilia; Risuleo, Gianfranco; Soula, Brigitte; Galibert, Anne-Marie; Flahaut, Emmanuel; Pinelli, Eric; Gauthier, Laury; Bianco, Alberto
2016-06-01
In the last few years, graphene has been defined as the revolutionary material showing an incredible expansion in industrial applications. Different graphene forms have been applied in several contexts, spreading from energy technologies and electronics to food and agriculture technologies. Graphene showed promises also in the biomedical field. Hopeful results have been already obtained in diagnostic, drug delivery, tissue regeneration and photothermal cancer ablation. In view of the enormous development of graphene-based technologies, a careful assessment of its impact on health and environment is demanded. It is evident how investigating the graphene toxicity is of fundamental importance in the context of medical purposes. On the other hand, the nanomaterial present in the environment, likely to be generated all along the industrial life-cycle, may have harmful effects on living organisms. In the present work, an important contribution on the impact of multi-layer graphene (MLG) on health and environment is given by using a multifaceted approach. For the first purpose, the effect of the material on two mammalian cell models was assessed. Key cytotoxicity parameters were considered such as cell viability and inflammatory response induction. This was combined with an evaluation of MLG toxicity towards Xenopus laevis, used as both in vivo and environmental model organism.
Ha, Jung-Yun; Chun, Ju-Na; Son, Jun Sik; Kim, Kyo-Han
2014-01-01
Dental modeling resins have been developed for use in areas where highly precise resin structures are needed. The manufacturers claim that these polymethyl methacrylate/methyl methacrylate (PMMA/MMA) resins show little or no shrinkage after polymerization. This study examined the polymerization shrinkage of five dental modeling resins as well as one temporary PMMA/MMA resin (control). The morphology and the particle size of the prepolymerized PMMA powders were investigated by scanning electron microscopy and laser diffraction particle size analysis, respectively. Linear polymerization shrinkage strains of the resins were monitored for 20 minutes using a custom-made linometer, and the final values (at 20 minutes) were converted into volumetric shrinkages. The final volumetric shrinkage values for the modeling resins were statistically similar (P > 0.05) or significantly larger (P < 0.05) than that of the control resin and were related to the polymerization kinetics (P < 0.05) rather than the PMMA bead size (P = 0.335). Therefore, the optimal control of the polymerization kinetics seems to be more important for producing high-precision resin structures rather than the use of dental modeling resins. PMID:24779020
Implementation of a flipped classroom educational model in a predoctoral dental course.
Park, Sang E; Howell, T Howard
2015-05-01
This article describes the development and implementation of a flipped classroom model to promote student-centered learning as part of a predoctoral dental course. This model redesigns the traditional lecture-style classroom into a blended learning model that combines active learning pedagogy with instructional technology and "flips" the sequence so that students use online resources to learn content ahead of class and then use class time for discussion. The dental anatomy portion of a second-year DMD course at Harvard School of Dental Medicine was redesigned using the flipped classroom model. The 36 students in the course viewed online materials before class; then, during class, small groups of students participated in peer teaching and team discussions based on learning objectives under the supervision of faculty. The utilization of pre- and post-class quizzes as well as peer assessments were critical motivating factors that likely contributed to the increase in student participation in class and helped place learning accountability on the students. Student feedback from a survey after the experience was generally positive with regard to the collaborative and interactive aspects of this form of blended learning. PMID:25941150
Low-shrinkage dental restorative composite: modeling viscoelastic behavior during setting.
Dauvillier, Bibi S; Feilzer, Albert J
2005-04-01
Much attention has been directed toward developing dental direct restorative composites that generate less shrinkage stress during setting. The aim of this study was to explore the viscoelastic behavior of a new class of low-shrinkage dental restorative composite during setting. The setting behavior of an experimental oxirane composite has been investigated by analyzing stress-strain data with two-parametric mechanical models. Experimental data were obtained from a dynamic test method, in which the setting light-activated composite was continuously subjected to sinusoidal strain cycles. The material parameters and the model's predictive capacity were analyzed with validated modeling procedures. The light-activated oxirane composite exhibited shrinkage delay and low polymerization shrinkage strain and stresses when compared with conventional light-activated composite. Noise in the stress data restricted the predictive ability of the Maxwell model to the elastic modulus development of the composite only. Evaluation tests of their potential as restorative material are required, to examine if the biocompatibility and mechanical properties after setting of oxirane composites are acceptable for dental use. PMID:15685614
Ashraf, Ali; Wu, Yanbin; Wang, Michael C; Aluru, Narayana R; Dastgheib, Seyed A; Nam, SungWoo
2014-11-01
We report the intrinsic water contact angle (WCA) of multilayer graphene, explore different methods of cleaning multilayer graphene, and evaluate the efficiency of those methods on the basis of spectroscopic analysis. Highly ordered pyrolytic graphite (HOPG) was used as a model material system to study the wettability of the multilayer graphene surface by WCA measurements. A WCA value of 45° ± 3° was measured for a clean HOPG surface, which can serve as the intrinsic WCA for multilayer graphene. A 1 min plasma treatment (100 W) decreased the WCA to 6°, owing to the creation of surface defects and functionalization by oxygen-containing groups. Molecular dynamics simulations of water droplets on the HOPG surface with or without the oxygen-containing defect sites confirmed the experimental results. Heat treatment at near atmospheric pressure and wet chemical cleaning methods using hydrofluoric acid and chloroform did not change the WCA significantly. Low-pressure, high-temperature annealing under argon and hydrogen reduced the WCA to 54°, close to the intrinsic WCA of HOPG. Raman spectroscopy and atomic force microscopy did not show any significant change for the HOPG surface after this treatment, confirming low-pressure, high-temperature annealing as an effective technique to clean multilayer graphene without damaging the surface. Time-of-flight secondary ion mass spectrometry indicated the existence of hydrocarbon species on the surface of the HOPG sample that was exposed to air for <5 min and the absence of these impurities in the bulk. X-ray photoelectron spectroscopy analyses of the sample surfaces after the different cleaning techniques were performed to correlate the WCA to the surface chemistry. X-ray photoelectron spectroscopy results revealed that the WCA value changed drastically, depending on the amounts of oxygen-containing and hydrocarbon-containing groups on the surface. PMID:25310520
Barone, Sandro; Paoli, Alessandro; Razionale, Armando Viviano
2015-07-01
In the field of orthodontic planning, the creation of a complete digital dental model to simulate and predict treatments is of utmost importance. Nowadays, orthodontists use panoramic radiographs (PAN) and dental crown representations obtained by optical scanning. However, these data do not contain any 3D information regarding tooth root geometries. A reliable orthodontic treatment should instead take into account entire geometrical models of dental shapes in order to better predict tooth movements. This paper presents a methodology to create complete 3D patient dental anatomies by combining digital mouth models and panoramic radiographs. The modeling process is based on using crown surfaces, reconstructed by optical scanning, and root geometries, obtained by adapting anatomical CAD templates over patient specific information extracted from radiographic data. The radiographic process is virtually replicated on crown digital geometries through the Discrete Radon Transform (DRT). The resulting virtual PAN image is used to integrate the actual radiographic data and the digital mouth model. This procedure provides the root references on the 3D digital crown models, which guide a shape adjustment of the dental CAD templates. The entire geometrical models are finally created by merging dental crowns, captured by optical scanning, and root geometries, obtained from the CAD templates. PMID:25670149
Recent Advances in Modeling Stress Distributions in Multilayers Subjected to Biaxial Flexure Tests
Hsueh, Chun-Hway; Luttrell, Claire Roberta
2007-01-01
Although biaxial flexure tests have been used extensively to measure the strength of brittle materials, the tests and analyses have been limited to materials of uniform properties. Despite the increasing applications of multilayered structures, characterization of their strengths using biaxial flexure tests has been difficult because the analytical description of the strength-fracture load relation for multilayers subjected to biaxial flexure tests is unavailable. The newly derived closed-form solutions for the elastic stress distributions in multilayered discs subjected to ring-on-ring tests are summarized here. These solutions are obtained by (i) finding the correlation between monolayered and multilayered discs subjected to biaxial bending moment and (ii) conversion from the existing solutions for monolayers. Using this methodology, the closed-form solutions for multilayers subjected to other biaxial flexure tests can also be obtained. Finite element results for ring-on-rings tests performed on (i) porcelain/zirconia bilayered discs and (ii) solid oxide fuel cells trilayered discs are also presented to validate the closed-form solutions. The closed-form solutions hence provide a basis for evaluating biaxial strength of multilayers using biaxial flexure tests.
Possibility of reconstruction of dental plaster cast from 3D digital study models
2013-01-01
Objectives To compare traditional plaster casts, digital models and 3D printed copies of dental plaster casts based on various criteria. To determine whether 3D printed copies obtained using open source system RepRap can replace traditional plaster casts in dental practice. To compare and contrast the qualities of two possible 3D printing options – open source system RepRap and commercially available 3D printing. Design and settings A method comparison study on 10 dental plaster casts from the Orthodontic department, Department of Stomatology, 2nd medical Faulty, Charles University Prague, Czech Republic. Material and methods Each of 10 plaster casts were scanned by inEos Blue scanner and the printed on 3D printer RepRap [10 models] and ProJet HD3000 3D printer [1 model]. Linear measurements between selected points on the dental arches of upper and lower jaws on plaster casts and its 3D copy were recorded and statistically analyzed. Results 3D printed copies have many advantages over traditional plaster casts. The precision and accuracy of the RepRap 3D printed copies of plaster casts were confirmed based on the statistical analysis. Although the commercially available 3D printing enables to print more details than the RepRap system, it is expensive and for the purpose of clinical use can be replaced by the cheaper prints obtained from RepRap printed copies. Conclusions Scanning of the traditional plaster casts to obtain a digital model offers a pragmatic approach. The scans can subsequently be used as a template to print the plaster casts as required. Using 3D printers can replace traditional plaster casts primarily due to their accuracy and price. PMID:23721330
NASA Astrophysics Data System (ADS)
Kim, Sung-Hee; Hong, Suk-Yoon; Song, Jee-Hun; Kil, Hyun-Gwon; Jeon, Jae Jin; Seo, Young-Soo
2012-06-01
Hull Mounted Sonar (HMS) is a long range submerged vehicle's hull-mounted passive sonar system which detects low-frequency noise caused by machineries of enemy ships or submerged vehicles. The HMS needs a sound absorption /insulation multi-layer structure to shut out the self-noise from own machineries and to amplify signals from outside. Therefore, acoustic analysis of the multi-layer system should be performed when the HMS is designed. This paper simplified the HMS multi-layer system to be an infinite planar multi-layer model. Also, main excitations that influence the HMS were classified into mechanical, plane wave and turbulent flow excitation, and the investigations for each excitation were performed for various models. Stiffened multi-layer analysis for mechanical excitation and general multi-layer analysis for turbulent flow excitation were developed. The infinite planar multi-layer analysis was expected to be more useful for preliminary design stage of HMS system than the infinite cylindrical model because of short analysis time and easiness of parameter study.
NASA Astrophysics Data System (ADS)
Lee, Keejoo
2005-11-01
A damage model for ceramic materials is developed and incorporated into the geometrically nonlinear solid shell element formulation for dynamic analyses of multi-layered ceramic armor panels under blast wave pressure loading. The damage model takes into account material behaviors observed from multi-axial dynamic tests on Aluminum Nitride (AlN) ceramic. The ceramic fails in a brittle or gradual fashion, depending upon the hydrostatic pressure and applied strain-rate. In the model, the gradual failure is represented by two states: the initial and final failure states. These states are described by two separate failure surfaces that are pressure-dependent and strain-rate-dependent. A scalar damage parameter is defined via using the two failure surfaces, based on the assumption that the local stress state determines material damage and its level. In addition, the damage model accounts for the effect of existing material damage on the new damage. The multi-layered armor panel of interest is comprised of an AlN-core sandwich with unidirectional composite skins and a woven composite back-plate. To accommodate the material damage effect of composite layers, a composite failure model in the open literature is adopted and modified into two separate failure models to address different failure mechanisms of the unidirectional and woven composites. In addition, the effect of strain-rates on the material strengths is incorporated into the composite failure models. For finite element modeling, multiple eighteen-node elements are used in the thickness direction to properly describe mechanics of the multi-layered panel. Dynamic analyses of a multi-layered armor panel are conducted under blast wave pressure loadings. The resulting dynamic responses of the panel demonstrate that dynamic analyses that do not take into account material damage and failure significantly under-predict the peak displacement. The under-prediction becomes more pronounced as the blast load level increases
NASA Astrophysics Data System (ADS)
Usenik, Peter; Bürmen, Miran; Fidler, Aleš; Pernuš, Franjo; Likar, Boštjan
2012-03-01
Despite major improvements in dental healthcare and technology, dental caries remains one of the most prevalent chronic diseases of modern society. The initial stages of dental caries are characterized by demineralization of enamel crystals, commonly known as white spots, which are difficult to diagnose. Near-infrared (NIR) hyperspectral imaging is a new promising technique for early detection of demineralization which can classify healthy and pathological dental tissues. However, due to non-ideal illumination of the tooth surface the hyperspectral images can exhibit specular reflections, in particular around the edges and the ridges of the teeth. These reflections significantly affect the performance of automated classification and visualization methods. Cross polarized imaging setup can effectively remove the specular reflections, however is due to the complexity and other imaging setup limitations not always possible. In this paper, we propose an alternative approach based on modeling the specular reflections of hard dental tissues, which significantly improves the classification accuracy in the presence of specular reflections. The method was evaluated on five extracted human teeth with corresponding gold standard for 6 different healthy and pathological hard dental tissues including enamel, dentin, calculus, dentin caries, enamel caries and demineralized regions. Principal component analysis (PCA) was used for multivariate local modeling of healthy and pathological dental tissues. The classification was performed by employing multiple discriminant analysis. Based on the obtained results we believe the proposed method can be considered as an effective alternative to the complex cross polarized imaging setups.
APPRAISAL OF ACCESS TO DENTAL SERVICES IN SOUTH EAST OF IRAN USING FIVE AS MODEL
Moosazadeh, Mahmood; Amiresmaili, Mohammadreza; Karimi, Sara; Arabpoor, Mahboobeh; Afshari, Mahdi
2016-01-01
Background: Access to dental services not only refers to utilization but also to the extent by which the utilization is judged according to professional norms. This study aimed to study the access to dental services using the Five As model. Methods: This cross sectional study was conducted in southeast of Iran. A sample of 400 subjects participated in the study according to a multistage sampling method. A questionnaire was used for data collection. Data were analyzed using independent T test, ANOVA and multivariate linear regression models by means of SPSS V.20 software. Findings: Affordability, availability, accessibility, accommodation and acceptability mean scores were 58.2±12.2, 53.9±12.9, 59.4±15.7, 60.2±8.6, 70±11.5 and 60.3±7.4 respectively. According to multivariate linear regression models, there was significant associations between affordability and age, education level, having basic insurance and family income. Moreover, total accessibility was significantly correlated with education and monthly family income. Conclusion: This study showed that access to dental services was at the moderate level among the studied population. It also revealed that age, basic insurance coverage, family income and level of education, are determinants of this accessibility. PMID:27482161
Nasedkina, A.A.; Nasedkin, A.V.; Iovane, G.
2009-07-15
The paper discusses modeling of a multi-layer coal seam under hydrodynamic action based on the coupled equations of poroelasticity and filtration with the nonlinear relationship of permeability and porous pressure. The calculations by the finite element method use correspondence between the poroelasticity and thermoelasticity equations. The influence of input data on the size of a degassing hole area is analyzed for the couple problem and pure filtration problem.
Implementation of a Multi-Layer Soil Model Into Biome-BGC - Calibration and Application
NASA Astrophysics Data System (ADS)
Puhlmann, M.; Jochheim, H.
2007-05-01
As a consequence of global warming the average annual temperature in the federal state of Brandenburg, Germany will probably increase by about 3 degrees Celsius until the end of the current century. Furthermore, precipitation is expected to shift from summer to winter. 35 % of Brandenburg is covered with forests, predominantly pine (P. sylvestris) accompanied by oak (Q. robur, Q. petraea) and beech (F. sylvatica). The forests are mainly located at sandy and loamy substrates with a low available water capacity. Hence, with an increase in temperature and a decrease in summer precipitation, water stress will occur more frequently or prolonged. This may lead to an alteration in groundwater recharge and tree composition and will be important for establishing sustainable forest management concepts. For an improved estimation of the potential effects of increased water stress on forests in Brandenburg, the one layer soil model of the biogeochemical and ecophysiological model Biome-BGC was replaced by a one dimensional multi-layer approach with an arbitrary number of soil layers of variable layer thickness. The model changes cover particularly soil hydrology and soil temperature processes, but also decomposition and the distribution of soil organic matter. Additional changes were implemented for enabling downward root growth and an improved interaction between vegetation and soil related water processes. The improved Biome-BGC model was calibrated by using data of a beech and a pine stand in north-eastern Brandenburg. Besides stand information (C and N stocks, growth measurements, etc.) and detailed soil information (horizon specific soil parameters), sap flow and throughfall measurements were available. Weather data were provided by nearby weather stations. With a focus on soil water budget, the most important results of the calibration will be shown. Furthermore, a global warming scenario simulation was carried out using a data set which is based on the A1B IPCC
NASA Astrophysics Data System (ADS)
Aguayo, M.; Marshall, H.; McNamara, J. P.; Mead, J.; Flores, A. N.
2013-12-01
Estimation of snowpack parameters such as depth, density and grain structure is a central focus of hydrology in seasonally snow-covered lands. These parameters are directly estimated by field observations, indirectly estimated from other parameters using statistical correlations, or simulated with a model. Difficulty in sampling thin layers and uncertainty in the transition between layers can cause significant uncertainty in measurements of these parameters. Snow density is one of the most important parameters to measure because it is strictly related with snow water content, an important component of the global water balance. We develop a mathematical framework to estimate snow density from measurements of temperature and thickness of snowpack layers over a particular time period, in conjunction with a physics-based model of snowpack evolution. We formulate a Bayesian approach to estimate the snowpack density profile, using a full range of possible simulations that incorporate key sources of uncertainty to build in prior snowpack knowledge. The posterior probability density function of the snow density, conditioned on snowpack temperature measurements, is computed by multiplying the likelihoods and assumed prior distribution function. Random sampling is used to generate a range of densities with same probability when prior uniform probability function is assumed. A posterior probability density function calculated directly via Bayes' theorem is used to calculate the probability of every sample generated. The forward model is a 1D, multilayer snow energy and mass balance model, which solves for snow temperature, density, and liquid water content on a finite element mesh. The surface and ground temperature data of snowpack (boundary conditions), are provided by the Center for Snow and Avalanche Studies (CSAS), Silverton CO, from snow pits made at Swamp Angel and Senator Beck study plot sites. Standard errors between field observations and results computed denote the
NASA Astrophysics Data System (ADS)
Iaquinta, Jean; Pinty, Bernard
1997-06-01
Multiangular data which will be available with the upcoming satellite platforms (EOS, ENVISAT, ADEOS) offer a great potential for monitoring land surfaces on the global scale to the extent that physically based models describing the transfer of radiation can be developed. The present study constitutes an additional step toward modeling this radiative transfer with in particular the physical processes involved at the boundary between land vegetated surfaces and the atmospheric layer above. Our primary objectives are to address issues related to the perturbation by an atmospheric layer of the solar radiance field incident on the top of the vegetation canopy and the interpretation of the radiance field emerging from the atmospheric layer when isotropic scattering from the surface is a priori assumed. Indeed, the application of an inappropriate model for the interpretation of remotely sensed data can produce inaccurate retrievals of both the surface and atmosphere characteristics. In the present study the radiation transport problem in this coupled system is solved analytically for uncollided and first collided radiation and uses a discrete ordinates method for multiple-scattered radiation. A sensitivity analysis of the multilayered ice-water-aerosol-vegetation-soil model is conducted in order to quantify the effects of atmospheric and surface perturbations within the whole system. The results are essentially reported in terms of bidirectional reflectance factors at visible and near-infrared wavelengths, which allows the use of very different radiative properties of the vegetation layer. The consequences of assumptions made on one or the other of these media are investigated through an inversion experiment.
Ben Daya, Ibrahim; Chen, Albert I. H.; Shafiee, Mohammad Javad; Wong, Alexander; Yeow, John T. W.
2015-01-01
3-D ultrasound imaging offers unique opportunities in the field of non destructive testing that cannot be easily found in A-mode and B-mode images. To acquire a 3-D ultrasound image without a mechanically moving transducer, a 2-D array can be used. The row column technique is preferred over a fully addressed 2-D array as it requires a significantly lower number of interconnections. Recent advances in 3-D row-column ultrasound imaging systems were largely focused on sensor design. However, these imaging systems face three intrinsic challenges that cannot be addressed by improving sensor design alone: speckle noise, sparsity of data in the imaged volume, and the spatially dependent point spread function of the imaging system. In this paper, we propose a compensated row-column ultrasound image reconstruction system using Fisher-Tippett multilayered conditional random field model. Tests carried out on both simulated and real row-column ultrasound images show the effectiveness of our proposed system as opposed to other published systems. Visual assessment of the results show our proposed system’s potential at preserving detail and reducing speckle. Quantitative analysis shows that our proposed system outperforms previously published systems when evaluated with metrics such as Peak Signal to Noise Ratio, Coefficient of Correlation, and Effective Number of Looks. These results show the potential of our proposed system as an effective tool for enhancing 3-D row-column imaging. PMID:26658577
NASA Astrophysics Data System (ADS)
Roy, H.; Chandraker, S.; Dutt, J. K.; Roy, T.
2016-05-01
Inherent material damping plays a very significant role on dynamic behaviour of rotors. The material damping in a spinning rotor produces a tangential force along the whirl direction and its magnitude being proportional to spin speed. After certain value of spin speed, decided by the characteristic of the system, the tangential force becomes strong enough to throw the rotor centre out of the whirl orbit by inflating it progressively. This leads to destabilization of the system and corresponding speed is known as stability limit of spin speed. Stability limit of spin speed for Jeffcott rotor, by using viscous form of material damping model is straight forward and has been reported by several researchers, however the same analysis for viscoelastic material characteristics is not reported much. This analysis is very relevant for industrial requirements to replace bulky and heavy metal rotor by light but strong rotors. This is achieved either by reinforcing fibre or multi layering arrangements. Both of which are represented by viscoelastic constitutive behaviour. This paper gives mathematical derivation of equations of motion for multi-disc, multi-layered rotor-shaft-system. Both lumped mass and discretized approach (finite element) are presented here mathematically and numerical simulation results are compared. The lumped mass approach gives a concise yet acceptable accuracy of the results.
Model independent x-ray standing wave analysis of periodic multilayer structures
Yakunin, S. N.; Pashaev, E. M.; Subbotin, I. A.; Makhotkin, I. A.; Kruijs, R. W. E. van de; Zoethout, E.; Chuev, M. A.; Louis, E.; Seregin, S. Yu.; Novikov, D. V.; Bijkerk, F.; Kovalchuk, M. V.
2014-04-07
We present a model independent approach for the analysis of X-ray fluorescence yield modulated by an X-ray standing wave (XSW), that allow a fast reconstruction of the atomic distribution function inside a sample without fitting procedure. The approach is based on the direct regularized solution of the system of linear equations that characterizes the fluorescence yield. The suggested technique was optimized for, but not limited to, the analysis of periodic layered structures where the XSW is formed under Bragg conditions. The developed approach was applied to the reconstruction of the atomic distribution function for LaN/BN multilayers with 50 periods of 43 Å thick layers. The object is especially difficult to analyze with traditional methods, as the estimated thickness of the interface region between the constituent materials is comparable to the individual layer thicknesses. However, using the suggested technique, it was possible to reconstruct width of the La atomic distribution showing that the La atoms stay localized within the LaN layers and interfaces and do not diffuse into the BN layer. The analysis of the reconstructed profiles showed that the positions of the center of the atomic distribution function can be estimated with an accuracy of 1 Å.
Development and Evaluation of an Endodontic Simulation Model for Dental Students.
Wolgin, Michael; Wiedemann, Paul; Frank, Wilhelm; Wrbas, Karl-Thomas; Kielbassa, Andrej M
2015-11-01
The aims of this study were to develop an endodontic simulation model able to implement the electronic method of working length determination (electronic apex locators, EALs) in a dental school, to evaluate the practicality of this tool for dental students, and to compare the accuracy of working length measurements achieved by the EAL and the radiographic method. A new simulation model was constructed by embedding extracted human teeth in a self-cured resin, along with a conductive medium. After radiographic and electronic working length determinations, root canal instrumentation was performed by students at a dental school in Austria according to the working lengths obtained from the EAL. Subsequently, root apices (n=44) were longitudinally sectioned using a diamond coated bur. Measurements of the distance between the anatomical root apex (ARA) and the apical constriction (AC) as well as between ARA and the ascertained apical point of endodontic instrumentation were performed using digital photography and a 3D computer-assisted design software. The distance between ARA and the radiologic (ARA-R) or electrometric (ARA-EL) readings of the apical point of endodontic instrumentation was compared with the actual distance ARA-AC. The accuracy of both methods was determined. The difference between the actual distance ARA-AC and the targeted radiological distance was statistically significant (p=0.0001), as was the measured distance between ARA-R and ARA-EL (p=0.016). The electronic method seems to be more precisely referring to the AC (R(2)=0.0198) than the radiographic method (R(2)=0.0019). These results suggest that the endodontic simulation model described in this study can be successfully used in preclinical dental education. PMID:26522643
NASA Astrophysics Data System (ADS)
Reed, Heather; Hoppe, Wally
2016-02-01
Thermographic NDE approaches to detect subsurface corrosion defects of multi-layered structures with composite top layers have proven difficult due to the fact that the thermal conductivity of composite materials is larger in lateral directions (the plane parallel to the surface) than in the through-thickness directions. This causes heat to dissipate faster laterally than through the thickness when a heat source is applied to the surface of the structure, making it difficult for subsurface damage effects to manifest on the surface, where the heat source and inspection typically occur. To address this, a heat induction approach is presented that excites the damaged, metallic bottom layer directly by Joule heating, resulting in more observable damage effects on the surface than what could be expected for traditional thermographic methods on this type of structure. To characterize the subsurface damage parameters (defect location, diameter, and depth), Bayesian inversion of numerically-simulated noisy data, using a high-fidelity, coupled electromagnetic-heat transfer model is employed. Stochastic estimation methods such as Markov chain Monte Carlo (MCMC) allow for quantification of uncertainty surrounding the damage parameters, which is important as this directly translates into uncertainty surrounding the component reliability. However, because thousands of high-fidelity finite element models are computationally costly to evaluate, as is typical in most MCMC methods, the use of Bayesian inversion is rarely feasible in real-time. To address this, a projection-based reduced order modeling (ROM) tracking and interpolation scheme is formulated within the MCMC sampling method for the multi-physics problem, resulting in significant speedup of solution time with little loss of accuracy, enabling near-real time stochastic estimation of damage.
Modeling the electromechanical impedance technique for the assessment of dental implant stability.
LaMalfa Ribolla, Emma; Rizzo, Piervincenzo
2015-07-16
We simulated the electromechanical impedance (EMI) technique to assess the stability of dental implants. The technique consists of bonding a piezoelectric transducer to the element to be monitored. When subjected to an electric field, the transducer induces structural excitations which, in turn, affect the transducer's electrical admittance. As the structural vibrations depend on the mechanical impedance of the element, the measurement of the transducer's admittance can be exploited to assess the element's health. In the study presented in this paper, we created a 3D finite element model to mimic a transducer bonded to the abutment of a dental implant placed in a host bone site. We simulated the healing that occurs after surgery by changing Young's modulus of the bone-implant interface. The results show that as Young's modulus of the interface increases, i.e. as the mechanical interlock of the implant within the bone is achieved, the electromechanical characteristic of the transducer changes. The model and the findings of this numerical study may be used in the future to predict and interpret experimental data, and to develop a robust and cost-effective method for the assessment of primary and secondary dental implant stability. PMID:26070645
A Fully Self-consistent Multi-layered Model of Jupiter
NASA Astrophysics Data System (ADS)
Kong, Dali; Zhang, Keke; Schubert, Gerald
2016-08-01
We construct a three-dimensional, fully self-consistent, multi-layered, non-spheroidal model of Jupiter consisting of an inner core, a metallic electrically conducting dynamo region, and an outer molecular electrically insulating envelope. We assume that the Jovian zonal winds are on cylinders parallel to the rotation axis but, due to the effect of magnetic braking, are confined within the outer molecular envelope. We also assume that the location of the molecular-metallic interface is characterized by its equatorial radius {{HR}}e, where R e is the equatorial radius of Jupiter at the 1 bar pressure level and H is treated as a parameter of the model. We solve the relevant mathematical problem via a perturbation approach. The leading-order problem determines the density, size, and shape of the inner core, the irregular shape of the 1 bar pressure level, and the internal structure of Jupiter that accounts for the full effect of rotational distortion, but without the influence of the zonal winds; the next-order problem determines the variation of the gravitational field solely caused by the effect of the zonal winds on the rotationally distorted non-spheroidal Jupiter. The leading-order solution produces the known mass, the known equatorial and polar radii, and the known zonal gravitational coefficient J 2 of Jupiter within their error bars; it also yields the coefficients J 4 and J 6 within about 5% accuracy, the core equatorial radius 0.09{R}e and the core density {ρ }c=2.0× {10}4 {{kg}} {{{m}}}-3 corresponding to 3.73 Earth masses; the next-order solution yields the wind-induced variation of the zonal gravitational coefficients of Jupiter.
NASA Astrophysics Data System (ADS)
Niezgoda, M.; Rochais, D.; Enguehard, F.; Echegut, P.; Rousseau, B.
2011-11-01
This paper presents an original modeling approach that enables the calculation of the temperature field within multilayer materials submitted to the flash method. The model takes into account the time-resolved coupled conducto-radiative heat transfer and the temperature of experiments. The compound can be subdivided into as many layers as desired, and their thicknesses and relevant physical properties can be chosen arbitrarily. Unconventional experimental thermograms can be reproduced faithfully by the calculations. This model, thus, makes it possible to correctly estimate the effective thermal diffusivity of semitransparent materials, thereby providing a deeper insight into the analysis of the physical phenomena involved.
A Finite Difference Method for Modeling Migration of Impurities in Multilayer Systems
NASA Astrophysics Data System (ADS)
Tosa, V.; Kovacs, Katalin; Mercea, P.; Piringer, O.
2008-09-01
A finite difference method to solve the one-dimensional diffusion of impurities in a multilayer system was developed for the special case in which a partition coefficient K impose a ratio of the concentrations at the interface between two adiacent layers. The fictitious point method was applied to derive the algebraic equations for the mesh points at the interface, while for the non-uniform mesh points within the layers a combined method was used. The method was tested and then applied to calculate migration of impurities from multilayer systems into liquids or solids samples, in migration experiments performed for quality testing purposes. An application was developed in the field of impurities migrations from multilayer plastic packagings into food, a problem of increasing importance in food industry.
NASA Astrophysics Data System (ADS)
Subeihi, Haitham
Multiscale Simulation and Modeling of Multilayer Heteroepitactic Growth of C60 on Pentacene.
Acevedo, Yaset M; Cantrell, Rebecca A; Berard, Philip G; Koch, Donald L; Clancy, Paulette
2016-03-29
We apply multiscale methods to describe the strained growth of multiple layers of C60 on a thin film of pentacene. We study this growth in the presence of a monolayer pentacene step to compare our simulations to recent experimental studies by Breuer and Witte of submonolayer growth in the presence of monolayer steps. The molecular-level details of this organic semiconductor interface have ramifications on the macroscale structural and electronic behavior of this system and allow us to describe several unexplained experimental observations for this system. The growth of a C60 thin film on a pentacene surface is complicated by the differing crystal habits of the two component species, leading to heteroepitactical growth. In order to probe this growth, we use three computational methods that offer different approaches to coarse-graining the system and differing degrees of computational efficiency. We present a new, efficient reaction-diffusion continuum model for 2D systems whose results compare well with mesoscale kinetic Monte Carlo (KMC) results for submonolayer growth. KMC extends our ability to simulate multiple layers but requires a library of predefined rates for event transitions. Coarse-grained molecular dynamics (CGMD) circumvents KMC's need for predefined lattices, allowing defects and grain boundaries to provide a more realistic thin film morphology. For multilayer growth, in this particularly suitable candidate for coarse-graining, CGMD is a preferable approach to KMC. Combining the results from these three methods, we show that the lattice strain induced by heteroepitactical growth promotes 3D growth and the creation of defects in the first monolayer. The CGMD results are consistent with experimental results on the same system by Conrad et al. and by Breuer and Witte in which C60 aggregates change from a 2D structure at low temperature to 3D clusters along the pentacene step edges at higher temperatures. PMID:26937559
Fold interaction and wavelength selection in 3D models of multilayer detachment folding
NASA Astrophysics Data System (ADS)
Fernandez, Naiara; Kaus, Boris J. P.
2014-09-01
Many fold-and-thrust belts are dominated by folding and exhibit a fairly regular fold-spacing. Yet, in map-view, the aspect ratio of doubly-plunging anticlines varies considerably from very elongated, and sometimes slightly curved, cylindrical folds to nearly circular, dome-like structures. In addition, the fold spacing often varies significantly around an average value. So far, it remains unclear whether these features are consistent with a folding instability. Therefore, we here study the dynamics of multilayer detachment folding, process by which shortening can be accommodated in thin-skinned fold-and-thrust belts. We start by analysing the physics of this process by using both a semi-analytical thick plate theory and numerical simulations. Results show that several different folding modes occur, about half of which are affected by gravity and have a wavelength that depends on the background deformation rate. Non-dimensional expressions are derived that predict the dominant wavelength and growth rate of each of these folding modes and mechanical phase diagrams are presented that illustrate the applicability of each of the modes. Next, we perform 3D simulations and compare the results with those of 2D models and analytical theory. Both 2D and 3D numerical simulations have wavelengths that are in good agreement with the analytical predictions. In the high-resolution 3D simulations the lateral growth of folds is studied, in particular with respect to fold segment interactions and evolution of fold width-length aspect ratio. The numerical simulations show a number of similarities with the Fars region of the Zagros fold-and-thrust belt including a large range of fold aspect ratio and a normally distributed fold wavelength around a dominant one.
NASA Astrophysics Data System (ADS)
Chen, Yin-Chu; Ferracane, Jack L.; Prahl, Scott A.
2005-03-01
Photo-cured dental composites are widely used in dental practices to restore teeth due to the esthetic appearance of the composites and the ability to cure in situ. However, their complex optical characteristics make it difficult to understand the light transport within the composites and to predict the depth of cure. Our previous work showed that the absorption and scattering coefficients of the composite changed after the composite was cured. The static Monte Carlo simulation showed that the penetration of radiant exposures differed significantly for cured and uncured optical properties. This means that a dynamic model is required for accurate prediction of radiant exposure in the composites. The purpose of this study was to develop and verify a dynamic Monte Carlo (DMC) model simulating light propagation in dental composites that have dynamic optical properties while photons are absorbed. The composite was divided into many small cubes, each of which had its own scattering and absorption coefficients. As light passed through the composite, the light was scattered and absorbed. The amount of light absorbed in each cube was calculated using Beer's Law and was used to determine the next optical properties in that cube. Finally, the predicted total reflectance and transmittance as well as the optical property during curing were verified numerically and experimentally. Our results showed that the model predicted values agreed with the theoretical values within 1% difference. The DMC model results are comparable with experimental results within 5% differences.
Implementation of a 3d numerical model of a folded multilayer carbonate aquifer
NASA Astrophysics Data System (ADS)
Di Salvo, Cristina; Guyennon, Nicolas; Romano, Emanuele; Bruna Petrangeli, Anna; Preziosi, Elisabetta
2016-04-01
The main objective of this research is to present a case study of the numerical model implementation of a complex carbonate, structurally folded aquifer, with a finite difference, porous equivalent model. The case study aquifer (which extends over 235 km2 in the Apennine chain, Central Italy) provides a long term average of 3.5 m3/s of good quality groundwater to the surface river network, sustaining the minimum vital flow, and it is planned to be exploited in the next years for public water supply. In the downstream part of the river in the study area, a "Site of Community Importance" include the Nera River for its valuable aquatic fauna. However, the possible negative effects of the foreseen exploitation on groundwater dependent ecosystems are a great concern and model grounded scenarios are needed. This multilayer aquifer was conceptualized as five hydrostratigraphic units: three main aquifers (the uppermost unconfined, the central and the deepest partly confined), are separated by two locally discontinuous aquitards. The Nera river cuts through the two upper aquifers and acts as the main natural sink for groundwater. An equivalent porous medium approach was chosen. The complex tectonic structure of the aquifer requires several steps in defining the conceptual model; the presence of strongly dipping layers with very heterogeneous hydraulic conductivity, results in different thicknesses of saturated portions. Aquifers can have both unconfined or confined zones; drying and rewetting must be allowed when considering recharge/discharge cycles. All these characteristics can be included in the conceptual and numerical model; however, being the number of flow and head target scarce, the over-parametrization of the model must be avoided. Following the principle of parsimony, three steady state numerical models were developed, starting from a simple model, and then adding complexity: 2D (single layer), QUASI -3D (with leackage term simulating flow through aquitards) and
Sikka, M P; Ghosh, S; Mukhopadhyay, A
2016-09-01
The effectiveness of the compression treatment by a medical compression bandage is dependent on the pressure generated at the interface between the bandage and the skin. This pressure is called interface pressure or sub-bandage pressure. The performance of a bandage depends upon the level of interface pressure applied by the bandage and the sustenance of this pressure over time. The interface pressure exerted by the bandage depends on several other factors like limb shape or size, application technique, physical and structural properties of the bandage, physical activities taken by the patient, etc. The current understanding of how bandages apply pressure to a limb is based on the Law of Laplace, which states that tension in the walls of a container is dependent on both the pressure of the container's content and its radius. This concept was translated mathematically into equation relating pressure to tension and radius by Thomas. In addition, a modified equation was generated by multiplying the model with a constant that represents the number of bandage layers in order to use the model to estimate the pressure applied by multi-layer bandages. This simple multiplication adjustment was questioned by researchers. They had doubts about the model validity and whether it can be used to predict the sub-bandage pressure applied by pressure garments. One of the questions that were raised regarding the bandage thickness affecting the sub-bandage pressure has been recently explored by Al Khaburi where he used the thin and thick cylinder shell theory to study the effect of Multi Component Bandage's (MCB) thickness on the sub-bandage pressure. The model by Al Khaburi and the earlier models developed for pressure prediction are all based on calculations considering the cylindrical limb shapes although the human limb normally is wider at the calf and reduces in circumference towards the ankle. So in our approach, the bandage is assumed to take a conical shape during application
Transient thermal behavior of multilayer media: Modeling and application to stratified moulds
NASA Astrophysics Data System (ADS)
Lazard, M.
2006-07-01
Transient and steady-state heat transfer in multilayer media is investigated by the thermal quadrupole method. A semi-analytical solution is proposed for the cases of layers parallel or orthogonal to the main heat-flux direction. The principal application is the study of the effect of the brazing metal used in stratified steel moulds.
Multidimensional causal model of dental caries development in low-income preschool children.
Litt, M D; Reisine, S; Tinanoff, N
1995-01-01
Despite the decline in the incidence of dental caries in the United States over the past several years, the condition remains a significant problem for the nation's poor children. Efforts to identify the factors responsible for caries development in samples of children of low socioeconomic status have primarily focused on a limited number of variables, and those have been predominantly biological (mutans streptococci, for example). Resulting models of caries development have usually shown good sensitivity but poor specificity. They have had limited implications for treatment. In an effort to produce a comprehensive model of caries development, 184 low-income preschool children were clinically assessed for mutans streptococci and for decayed, missing, or filled surfaces of deciduous teeth twice, first at age 4 years (baseline) and again a year later (year 1 assessment). As the clinical assessments were being done, caretakers were being interviewed to obtain data from five domains: demographics, social status, dental health behaviors, cognitive factors such as self-efficacy (self-confidence) and controllability, and perceived life stress. Data were analyzed using a structural equations modeling approach in which variables from all domains, plus baseline decayed missing and filled surfaces and baseline mutants, were used together to create a model of caries development in the year 1 assessment. Results confirmed earlier work that suggested that caries development at a 1-year followup was strongly dependent on earlier caries development. Early caries development in this sample was determined in part by mutans levels and by dental health behaviors. These behaviors themselves were accounted for partly by a cognitive factor.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7480616
First Principles Modeling of Metal/Ceramic Multilayer Nano-heterostructures.
Yadav, Satyesh K.; Wang, Jian; Misra, Amit; Liu, Xiang-Yang; Ramprasad, Ramamurthy
2012-07-31
Nanoscaled multilayer films composed of metals and ceramics have been explored for their potential applications as ductile, yet strong, materials. It is believed that at the nanoscale, the interfaces between the two materials constituting the multilayer assume an increasingly important role in determining the properties, as they comprise a more significant volume fraction of the multilayer with decreasing layer thickness. In this ab initio work, density functional theory was used to calculate the ideal shear strengths of pure Al, pure TiN, the Al/TiN interfacial region, and Al/TiN multilayers. The ideal shear strength of the Al/TiN interface was found to vary from very low (on the order of the ideal shear strength of Al) to very high (on the order of the ideal shear strength of TiN), depending on whether the TiN at the interface was Ti- or N-terminated, respectively. The results suggest that the shear properties of Al/TiN depend strongly on the chemistry of the interface, Al:N versus Al:Ti terminations. Nevertheless, for the Al/TiN multilayers, the ideal shear strength was limited by shear in the Al layer away from the interface, even when the individual layer thickness is less than a nanometer. Further we found an unusual structural rotation of bulk single-crystal Al under uniaxial compressive strains. It was found that under strains either along the <11-2> or the <111> directions, beyond a critical stress of about 13 GPa, the Al crystal can rotate through shear in the Shockley partial direction (i.e.,<11-2>) on the {l_brace}111{r_brace} plane, in an attempt to relieve internal stresses. This phenomenon reveals a possible mechanism leading to the onset of homogeneous dislocation nucleation in Al under high uniaxial compressions.
Sato, Kimiko; Oda, Megumi
2011-04-01
A questionnaire survey was administered to 317 parents who attended infant health check-ups in City B, Okayama Prefecture between October, 2008 and March, 2009. The questionnaire survey studied 7 factors based on the PRECEDE-PROCEED Model. We analysed factors that affected oral health behaviour and attendance at scheduled dental health check-ups. The survey containing 22 items concerning matters such as 'QOL' and 'health problems' was posted to parents and guardians in advance, and then collected on the day of the medical check-up. The collected data was analysed using the t-test and Pearson's correlation coefficient, following which we conducted a covariance structure analysis. The results showed that dental health behaviour was directly affected by reinforcing factors, and indirectly associated with enabling and predisposing factors influenced by reinforcing factors. It was also shown that predisposing factors and oral health behaviour were associated with attendance at scheduled oral health check-ups. The results indicated that strengthening oral health education by sharing knowledge that acts as predisposing factors and introducing adaptations of oral health behaviour that that fit individual lives will lead to improved attendance at scheduled dental health check-ups. PMID:21519364
Dental education and dental practice.
Moore, J R
1984-01-01
This paper relates recent modes of dental practice to changes that the public and government are likely to ask the health care professions to make in the future. As usual they are asking for the best of all worlds. First, that we maintain the clinical model to the highest standards of personal dental care based and tested against the best research at our disposal, whilst we ensure there is no reduction in the high technical standards for which british dentists have a reputation. Second, that the profession is required to consider ways of providing care on the medicosocial model for the whole community at an economic level the country will afford. The broad changes in dental education have been reviewed, from the technical apprenticeship to the establishment of strong university departments in teaching hospitals. The importance of a sound biomedical foundation and of research both to education and the credibility of dental practice as a primary health care profession is stressed if the profession is to retain its position as a sister to medicine and not slide down to that of a technical ancillary. PMID:6374141
Ex Vivo Modeling of Multidomain Peptide Hydrogels with Intact Dental Pulp.
Moore, A N; Perez, S C; Hartgerink, J D; D'Souza, R N; Colombo, J S
2015-12-01
Preservation of a vital dental pulp is a central goal of restorative dentistry. Currently, there is significant interest in the development of tissue engineering scaffolds that can serve as biocompatible and bioactive pulp-capping materials, driving dentin bridge formation without causing cytotoxic effects. Our earlier in vitro studies described the biocompatibility of multidomain peptide (MDP) hydrogel scaffolds with dental pulp-derived cells but were limited in their ability to model contact with intact 3-dimensional pulp tissues. Here, we utilize an established ex vivo mandible organ culture model to model these complex interactions. MDP hydrogel scaffolds were injected either at the interface of the odontoblasts and the dentin or into the pulp core of mandible slices and subsequently cultured for up to 10 d. Histology reveals minimal disruption of tissue architecture adjacent to MDP scaffolds injected into the pulp core or odontoblast space. Additionally, the odontoblast layer is structurally preserved in apposition to the MDP scaffold, despite being separated from the dentin. Alizarin red staining suggests mineralization at the periphery of MDP scaffolds injected into the odontoblast space. Immunohistochemistry reveals deposition of dentin sialophosphoprotein by odontoblasts into the adjacent MDP hydrogel, indicating continued functionality. In contrast, no mineralization or dentin sialophosphoprotein deposition is evident around MDP scaffolds injected into the pulp core. Collagen III expression is seen in apposition to gels at all experimental time points. Matrix metalloproteinase 2 expression is observed associated with centrally injected MDP scaffolds at early time points, indicating proteolytic digestion of scaffolds. Thus, MDP scaffolds delivered centrally and peripherally within whole dental pulp tissue are shown to be biocompatible, preserving local tissue architecture. Additionally, odontoblast function and pulp vitality are sustained when MDP
... Data & Statistics > Find Data by Topic > Dental Sealants Dental Sealants Main Content Dental sealants are thin plastic coatings that protect the chewing surfaces of children’s back teeth from tooth decay. Overall, the prevalence of sealants ...
NASA Astrophysics Data System (ADS)
Wever, Nander; Würzer, Sebastian; Fierz, Charles; Lehning, Michael
2016-04-01
For physics based snow cover models, simulating the formation of dense ice layers inside the snowpack has been a long time challenge. In spite of their small vertical extend, the presence of ice lenses inside the snowpack can have a profound impact on vapor, heat and liquid water flow. These effects may ultimately influence processes on larger scales when, for example, looking at hydrological processes or wet snow avalanche formation. Also microwave emission signals from the snowpack are strongly influenced by the presence of ice layers. Recent laboratory experiments and modelling techniques of liquid water flow in snow have advanced the understanding of liquid water flow in snow, in particular the formation of preferential flow paths. We present a modelling approach in the one-dimensional, multi-layer snow cover model SNOWPACK for preferential flow that is based on a dual-domain approach (i.e., separation into a matrix flow and a preferential flow domain) and solving Richards equation for both. In recently published laboratory experiments, water ponding inside the snowpack has been identified to initiate preferential flow. Those studies also quantified the part of the snowpack involved in preferential flow as a function of grain size. By combining these concepts with an empirical function to determine refreezing of preferential flow water inside the snowpack, we are able to simulate preferential water flow in the model. We found that preferential flow paths arriving at a layer transition in the snowpack may lead to ponding conditions. Subsequent refreezing then may form dense ice layers (>700 kg/m3). We compare the simulations to 14 years of biweekly snow profiles made at the Weissfluhjoch study plot at 2540m altitude in the Eastern Swiss Alps. We show that we are able to reproduce several ice lenses that were observed in the field, whereas some profiles remain challenging to simulate.
Physical model for non-steady-state dissolution of dental enamel.
Patel, M V; Fox, J L; Higuchi, W I
1987-09-01
The purpose of this study was to provide a rigorous theoretical understanding of the dissolution behavior of dental enamel over the entire time-course of demineralization and to simulate by computer an erosion-type caries lesion according to the physical "hydroxyapatite model". The appropriate diffusion equations which account for simultaneous diffusion and equilibrium of all species in enamel pores, boundary layer, and bulk solution, and which also take into consideration surface reaction kinetics, were employed to allow for calculation of the micro-environmental solution concentration and changes in the mineral density as a function of time and distance within the enamel. This comprehensive physical model for non-steady-state enamel dissolution also explicitly takes into account changes in the diffusivity and the dissolution rate constant as a function of mineral density. Demineralization experiments were conducted in 0.1 mol/L sink acetate buffer (pH = 4.50, mu = 0.50), with ground bovine dental enamel blocks of known surface area mounted (with beeswax) in a rotating disk apparatus. Mineral density profiles were quantified by means of contact x-ray microradiography. The physical model was used to predict mineral density profiles for given demineralization treatments. The experimental profiles agreed quite well with the predicted profiles, when the effective diffusivity of the enamel was assumed to be a function of porosity and when changes in surface area of the crystallites were taken into consideration. PMID:3476613
Ramponi, Denise R
2016-01-01
Dental problems are a common complaint in emergency departments in the United States. There are a wide variety of dental issues addressed in emergency department visits such as dental caries, loose teeth, dental trauma, gingival infections, and dry socket syndrome. Review of the most common dental blocks and dental procedures will allow the practitioner the opportunity to make the patient more comfortable and reduce the amount of analgesia the patient will need upon discharge. Familiarity with the dental equipment, tooth, and mouth anatomy will help prepare the practitioner for to perform these dental procedures. PMID:27482994
SSIC model: A multi-layer model for intervention of online rumors spreading
NASA Astrophysics Data System (ADS)
Tian, Ru-Ya; Zhang, Xue-Fu; Liu, Yi-Jun
2015-06-01
SIR model is a classical model to simulate rumor spreading, while the supernetwork is an effective tool for modeling complex systems. Based on the Opinion SuperNetwork involving Social Sub-network, Environmental Sub-network, Psychological Sub-network, and Viewpoint Sub-network, drawing from the modeling idea of SIR model, this paper designs super SIC model (SSIC model) and its evolution rules, and also analyzes intervention effects on public opinion of four elements of supernetwork, which are opinion agent, opinion environment, agent's psychology and viewpoint. Studies show that, the SSIC model based on supernetwork has effective intervention effects on rumor spreading. It is worth noting that (i) identifying rumor spreaders in Social Sub-network and isolating them can achieve desired intervention results, (ii) improving environmental information transparency so that the public knows as much information as possible to reduce the rumors is a feasible way to intervene, (iii) persuading wavering neutrals has better intervention effects than clarifying rumors already spread everywhere, so rumors should be intervened in properly in time by psychology counseling.
Limit analysis of multi-layered plates. Part I: The homogenized Love-Kirchhoff model
NASA Astrophysics Data System (ADS)
Dallot, Julien; Sab, Karam
The purpose of this paper is to determine Gphom, the overall homogenized Love-Kirchhoff strength domain of a rigid perfectly plastic multi-layered plate, and to study the relationship between the 3D and the homogenized Love-Kirchhoff plate limit analysis problems. In the Love-Kirchhoff model, the generalized stresses are the in-plane (membrane) and the out-of-plane (flexural) stress field resultants. The homogenization method proposed by Bourgeois [1997. Modélisation numérique des panneaux structuraux légers. Ph.D. Thesis, University Aix-Marseille] and Sab [2003. Yield design of thin periodic plates by a homogenization technique and an application to masonry wall. C. R. Méc. 331, 641-646] for in-plane periodic rigid perfectly plastic plates is justified using the asymptotic expansion method. For laminated plates, an explicit parametric representation of the yield surface ∂Gphom is given thanks to the π-function (the plastic dissipation power density function) that describes the local strength domain at each point of the plate. This representation also provides a localization method for the determination of the 3D stress components corresponding to every generalized stress belonging to ∂Gphom. For a laminated plate described with a yield function of the form F(x3,σ)=σu(x3)F^(σ), where σu is a positive even function of the out-of-plane coordinate x3 and F^ is a convex function of the local stress σ, two effective constants and a normalization procedure are introduced. A symmetric sandwich plate consisting of two Von-Mises materials ( σu=σ1u in the skins and σu=σ2u in the core) is studied. It is found that, for small enough contrast ratios ( r=σ1u/σ2u≤5), the normalized strength domain G^phom is close to the one corresponding to a homogeneous Von-Mises plate [Ilyushin, A.-A., 1956. Plasticité. Eyrolles, Paris].
NASA Astrophysics Data System (ADS)
Chen, Zhao-Jiang; Zhang, Shu-Yi
2010-02-01
A new hybrid inversion method for depth profiling reconstruction of thermal conductivities of inhomogeneous solids is proposed based on multilayer quadrupole formalism of thermal waves, particle swarm optimization and sequential quadratic programming. The reconstruction simulations for several thermal conductivity profiles are performed to evaluate the applicability of the method. The numerical simulations demonstrate that the precision and insensitivity to noise of the inversion method are very satisfactory.
NASA Technical Reports Server (NTRS)
Li, Peng; Chou, Ming-Dah; Arking, Albert
1987-01-01
The transient response of the climate to increasing CO2 is studied using a modified version of the multilayer energy balance model of Peng et al. (1982). The main characteristics of the model are described. Latitudinal and seasonal distributions of planetary albedo, latitude-time distributions of zonal mean temperatures, and latitudinal distributions of evaporation, water vapor transport, and snow cover generated from the model and derived from actual observations are analyzed and compared. It is observed that in response to an atmospheric doubling of CO2, the model reaches within 1/e of the equilibrium response of global mean surface temperature in 9-35 years for the probable range of vertical heat diffusivity in the ocean. For CO2 increases projected by the National Research Council (1983), the model's transient response in annually and globally averaged surface temperatures is 60-75 percent of the corresponding equilibrium response, and the disequilibrium increases with increasing heat diffusivity of the ocean.
NASA Astrophysics Data System (ADS)
Huang, Wei; Zhang, Xingnan; Li, Chenming; Wang, Jianying
Management of group decision-making is an important issue in water source management development. In order to overcome the defects in lacking of effective communication and cooperation in the existing decision-making models, this paper proposes a multi-layer dynamic model for coordination in water resource allocation and scheduling based group decision making. By introducing the scheme-recognized cooperative satisfaction index and scheme-adjusted rationality index, the proposed model can solve the problem of poor convergence of multi-round decision-making process in water resource allocation and scheduling. Furthermore, the problem about coordination of limited resources-based group decision-making process can be solved based on the effectiveness of distance-based group of conflict resolution. The simulation results show that the proposed model has better convergence than the existing models.
Federal Register 2010, 2011, 2012, 2013, 2014
2012-04-05
... COMMISSION Certain Digital Models, Digital Data, and Treatment Plans for Use in Making Incremental Dental Positioning Adjustment Appliances, the Appliances Made Therefrom, and Methods of Making the Same; Institution... of certain digital models, digital data, and treatment plans for use in making incremental...
NASA Astrophysics Data System (ADS)
Humeida, Yousif; Pinfield, Valerie J.; Challis, Richard E.
2013-08-01
Ultrasonic arrays have seen increasing use for the characterisation of composite materials. In this paper, ultrasonic wave propagation in multilayer anisotropic materials has been modelled using plane wave and angular spectrum decomposition techniques. Different matrix techniques, such as the stiffness matrix method and the transfer matrix method, are used to calculate the reflection and transmission coefficients of ultrasonic plane waves in the considered media. Then, an angular decomposition technique is used to derive the bounded beams from finite-width ultrasonic array elements from the plane wave responses calculated earlier. This model is considered to be an analytical exact solution for the problem; hence the diffraction of waves in such composite materials can be calculated for different incident angles for a very wide range of frequencies. This model is validated against experimental measurements using the Full-Matrix Capture (FMC) of array data in both a homogeneous isotropic material, i.e. aluminium, and an inhomogeneous multilayer anisotropic material, i.e. a carbon fibre reinforced composite.
Biomechanical model produced from light-activated dental composite resins: a holographic analysis
NASA Astrophysics Data System (ADS)
Pantelić, Dejan; Vasiljević, Darko; Blažić, Larisa; Savić-Šević, Svetlana; Murić, Branka; Nikolić, Marko
2013-11-01
Light-activated dental composites, commonly applied in dentistry, can be used as excellent material for producing biomechanical models. They can be cast in almost any shape in an appropriate silicone mold and quickly solidified by irradiation with light in the blue part of the spectrum. In that way, it is possible to obtain any number of nearly identical casts. The models can be used to study the behavior of arbitrary structure under mechanical loads. To test the technique, a simple mechanical model of the tooth with a mesio-occluso-distal cavity was manufactured. Composite resin restoration was placed inside the cavity and light cured. Real-time holographic interferometry was used to analyze the contraction of the composite resin and its effect on the surrounding material. The results obtained in the holographic experiment were in good agreement with those obtained using the finite element method.
Modeling of viscoelastic behavior of dental chemically activated resin composites during curing.
Dauvillier, B S; Hübsch, P F; Aarnts, M P; Feilzer, A J
2001-01-01
Shrinkage stresses generated in dental resin composites during curing are among the major problems in adhesive dentistry, because they interfere with the integrity of the restored tooth. The aim of this study was to find a mechanical model to describe the viscoelastic behavior of a two-paste resin composite during curing, to aid our understanding of the process of shrinkage stress development. In this study, stress-strain data on Clearfil F2 during curing were obtained by a dynamic test method and analyzed using three mechanical models (Maxwell, Kelvin, and the Standard Linear Solid model). With a modeling procedure, the model's stress response was compared with the experimental stress data, and the material parameters were calculated. On the basis of the modeling and evaluation results, a model for describing the viscoelastic behavior of the shrinking resin composite was selected. The validation results showed that the modeling procedure is free of error, and that it was capable of finding material parameters associated with a two-parametric model with a high degree of accuracy. The viscoelastic behavior of the shrinking resin composite, as excited by the conditions of the test method, cannot be described by a single mechanical model. In the early stage of curing, the most accurate prediction was achieved by the Maxwell model, while during the remainder of the curing process the Kelvin model can be used to describe the viscoelastic behavior of the two-paste resin composite. PMID:11152993
d'Errico, Michele; Sammarco, Paolo; Vairo, Giuseppe
2015-09-01
Pharmacokinetics induced by drug eluting stents (DES) in coronary walls is modeled by means of a one-dimensional multi-layered model, accounting for vessel curvature and non-homogeneous properties of the arterial tissues. The model includes diffusion mechanisms, advection effects related to plasma filtration through the walls, and bio-chemical drug reactions. A non-classical Sturm-Liouville problem with discontinuous coefficients is derived, whose closed-form analytical solution is obtained via an eigenfunction expansion. Soundness and consistency of the proposed approach are shown by numerical computations based on possible clinical treatments involving both hydrophilic and hydrophobic drugs. The influence of the main model parameters on drug delivery mechanisms is analyzed, highlighting the effects induced by vessel curvature and yielding comparative indications and useful insights into the concurring mechanisms governing the pharmacokinetics. PMID:26162517
Statistical power of multilevel modelling in dental caries clinical trials: a simulation study.
Burnside, G; Pine, C M; Williamson, P R
2014-01-01
Outcome data from dental caries clinical trials have a naturally hierarchical structure, with surfaces clustered within teeth, clustered within individuals. Data are often aggregated into the DMF index for each individual, losing tooth- and surface-specific information. If these data are to be analysed by tooth or surface, allowing exploration of effects of interventions on different teeth and surfaces, appropriate methods must be used to adjust for the clustered nature of the data. Multilevel modelling allows analysis of clustered data using individual observations without aggregating data, and has been little used in the field of dental caries. A simulation study was conducted to investigate the performance of multilevel modelling methods and standard caries increment analysis. Data sets were simulated from a three-level binomial distribution based on analysis of a caries clinical trial in Scottish adolescents, with varying sample sizes, treatment effects and random tooth level effects based on trials reported in Cochrane reviews of topical fluoride, and analysed to compare the power of multilevel models and traditional analysis. 40,500 data sets were simulated. Analysis showed that estimated power for the traditional caries increment method was similar to that for multilevel modelling, with more variation in smaller data sets. Multilevel modelling may not allow significant reductions in the number of participants required in a caries clinical trial, compared to the use of traditional analyses, but investigators interested in exploring the effect of their intervention in more detail may wish to consider the application of multilevel modelling to their clinical trial data. PMID:24216573
Mahmood, Deyar Jallal Hadi; Linderoth, Ewa H; Wennerberg, Ann; Vult Von Steyern, Per
2016-01-01
Aim To investigate and compare the fracture strength and fracture mode in eleven groups of currently, the most commonly used multilayer three-unit all-ceramic yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) fixed dental prostheses (FDPs) with respect to the choice of core material, veneering material area, manufacturing technique, design of connectors, and radii of curvature of FDP cores. Materials and methods A total of 110 three-unit Y-TZP FDP cores with one intermediate pontic were made. The FDP cores in groups 1–7 were made with a split-file design, veneered with manually built-up porcelain, computer-aided design-on veneers, and over-pressed veneers. Groups 8–11 consisted of FDPs with a state-of-the-art design, veneered with manually built-up porcelain. All the FDP cores were subjected to simulated aging and finally loaded to fracture. Results There was a significant difference (P<0.05) between the core designs, but not between the different types of Y-TZP materials. The split-file designs with VITABLOCS® (1,806±165 N) and e.max® ZirPress (1,854±115 N) and the state-of-the-art design with VITA VM® 9 (1,849±150 N) demonstrated the highest mean fracture values. Conclusion The shape of a split-file designed all-ceramic reconstruction calls for a different dimension protocol, compared to traditionally shaped ones, as the split-file design leads to sharp approximal indentations acting as fractural impressions, thus decreasing the overall strength. The design of a framework is a crucial factor for the load bearing capacity of an all-ceramic FDP. The state-of-the-art design is preferable since the split-file designed cores call for a cross-sectional connector area at least 42% larger, to have the same load bearing capacity as the state-of-the-art designed cores. All veneering materials and techniques tested in the study, split-file, over-press, built-up porcelains, and glass–ceramics are, with a great safety margin, sufficient for clinical use
NASA Astrophysics Data System (ADS)
Nicola, Ester M. D.; Junqueira, Silvio L. M.; Busato, Mara S.
1994-09-01
Carbon dioxide laser has been used in dental surgery. The existence of healthy teeth, which have pulp vitality needing to be preserved, is observed in a great number of cases. In this work we describe an experimental model which provides the measurement of temperature in pulp chamber `in vivo,' during oral surgeries in which the CO2 laser beam is applied to gingival tissue. The problems met during the search for the best way to place the thermal probe regarding the diameter and depth of pulp chamber and the thickness of the tissue layer formed by gum and maxillary bone are discussed. We use a thermocouple placed in the pulp chamber of superior canine teeth in dogs. After that, the probe was also placed between gum and dental root. Since the temperature at gingival surface was known, it was easy to determine the rise in temperature at pulp chamber and also to observe the thermal gradient from gum to tissue to bone, thus avoiding pulp damage during laser applications.
Modeling dental composite shrinkage by digital image correlation and finite element methods
NASA Astrophysics Data System (ADS)
Chen, Terry Yuan-Fang; Huang, Pin-Sheng; Chuang, Shu-Fen
2014-10-01
Dental composites are light-curable resin-based materials with an inherent defect of polymerization shrinkage which may cause tooth deflection and debonding of restorations. This study aimed to combine digital image correlation (DIC) and finite element analysis (FEA) to model the shrinkage behaviors under different light curing regimens. Extracted human molars were prepared with proximal cavities for composite restorations, and then divided into three groups to receive different light curing protocols: regular intensity, low intensity, and step-curing consisting of low and high intensities. For each tooth, the composite fillings were consecutively placed under both unbonded and bonded conditions. At first, the shrinkage of the unbonded restorations was analyzed by DIC and adopted as the setting of FEA. The simulated shrinkage behaviors obtained from FEA were further validated by the measurements in the bonded cases. The results showed that different light curing regimens affected the shrinkage in unbonded restorations, with regular intensity showing the greatest shrinkage strain on the top surface. The shrinkage centers in the bonded cases were located closer to the cavity floor than those in the unbonded cases, and were less affected by curing regimens. The FEA results showed that the stress was modulated by the accumulated light energy density, while step-curing may alleviate the tensile stress along the cavity walls. In this study, DIC provides a complete description of the polymerization shrinkage behaviors of dental composites, which may facilitate the stress analysis in the numerical investigation.
Framework for e-learning assessment in dental education: a global model for the future.
Arevalo, Carolina R; Bayne, Stephen C; Beeley, Josie A; Brayshaw, Christine J; Cox, Margaret J; Donaldson, Nora H; Elson, Bruce S; Grayden, Sharon K; Hatzipanagos, Stylianos; Johnson, Lynn A; Reynolds, Patricia A; Schönwetter, Dieter J
2013-05-01
The framework presented in this article demonstrates strategies for a global approach to e-curricula in dental education by considering a collection of outcome assessment tools. By combining the outcomes for overall assessment, a global model for a pilot project that applies e-assessment tools to virtual learning environments (VLE), including haptics, is presented. Assessment strategies from two projects, HapTEL (Haptics in Technology Enhanced Learning) and UDENTE (Universal Dental E-learning), act as case-user studies that have helped develop the proposed global framework. They incorporate additional assessment tools and include evaluations from questionnaires and stakeholders' focus groups. These measure each of the factors affecting the classical teaching/learning theory framework as defined by Entwistle in a standardized manner. A mathematical combinatorial approach is proposed to join these results together as a global assessment. With the use of haptic-based simulation learning, exercises for tooth preparation assessing enamel and dentine were compared to plastic teeth in manikins. Equivalence for student performance for haptic versus traditional preparation methods was established, thus establishing the validity of the haptic solution for performing these exercises. Further data collected from HapTEL are still being analyzed, and pilots are being conducted to validate the proposed test measures. Initial results have been encouraging, but clearly the need persists to develop additional e-assessment methods for new learning domains. PMID:23658401
Dental impaction pain model as a potential tool to evaluate drugs with efficacy in neuropathic pain.
Malmstrom, Kerstin; Kotey, Paul; McGratty, Megan; Ramakrishnan, Rohini; Gottesdiener, Keith; Reicin, Alise; Wagner, John A
2006-08-01
Intravenous lidocaine, a nonspecific Na-channel blocker, was used to assess the dental impaction model for evaluation of neuropathic pain drugs. Sixty patients, experiencing moderate or severe pain after removal of > or = 2 third molars, were randomized (2:2:1:1) to lidocaine (4 mg/kg; maximal dose 300 mg), oxycodone/acetaminophen (10/650 mg), placebo, and active placebo (diphenhydramine, 50 mg). Lidocaine provided a modest degree of pain relief. Predefined endpoints of total pain relief and sum of pain intensity at 2, 4, and 6 hours showed numerically, not statistically significantly, greater pain relief versus placebo. A significantly greater effect over placebo was observed in peak effect and at shorter time points (30 minutes and 1 hour), consistent with the pharmacokinetic profile (plasma concentration of approximately 2 mug/mL). Oxycodone/acetaminophen provided significantly greater analgesia versus placebo, validating study conduct, and significantly greater pain relief was observed versus lidocaine, which is consistent with a smaller portion of dental extraction pain being of neuropathic origin. PMID:16855076
NASA Astrophysics Data System (ADS)
WöHling, Thomas; Vrugt, Jasper A.
2011-04-01
In the past two decades significant progress has been made toward the application of inverse modeling to estimate the water retention and hydraulic conductivity functions of the vadose zone at different spatial scales. Many of these contributions have focused on estimating only a few soil hydraulic parameters, without recourse to appropriately capturing and addressing spatial variability. The assumption of a homogeneous medium significantly simplifies the complexity of the resulting inverse problem, allowing the use of classical parameter estimation algorithms. Here we present an inverse modeling study with a high degree of vertical complexity that involves calibration of a 25 parameter Richards'-based HYDRUS-1D model using in situ measurements of volumetric water content and pressure head from multiple depths in a heterogeneous vadose zone in New Zealand. We first determine the trade-off in the fitting of both data types using the AMALGAM multiple objective evolutionary search algorithm. Then we adopt a Bayesian framework and derive posterior probability density functions of parameter and model predictive uncertainty using the recently developed differential evolution adaptive metropolis, DREAMZS adaptive Markov chain Monte Carlo scheme. We use four different formulations of the likelihood function each differing in their underlying assumption about the statistical properties of the error residual and data used for calibration. We show that AMALGAM and DREAMZS can solve for the 25 hydraulic parameters describing the water retention and hydraulic conductivity functions of the multilayer heterogeneous vadose zone. Our study clearly highlights that multiple data types are simultaneously required in the likelihood function to result in an accurate soil hydraulic characterization of the vadose zone of interest. Remaining error residuals are most likely caused by model deficiencies that are not encapsulated by the multilayer model and can not be accessed by the
NASA Astrophysics Data System (ADS)
Kim, Do-Hyoung; Joo, Sung-Jun; Kwak, Dong-Ok; Kim, Hak-Sung
2015-10-01
In this study, the warpage simulation of a multi-layer printed circuit board (PCB) was performed as a function of various copper (Cu) patterns/photoimageable solder resist (PSR) composite patterns and their anisotropic viscoelastic properties. The thermo-mechanical properties of Cu/PSR patterns were obtained from finite element analysis (virtual test) and homogenized with anisotropic composite shell models that considered the viscoelastic properties. The multi-layer PCB model was simplified based on the unit Cu/PSR patterns and the warpage simulation during the reflow process was performed by using ABAQUS combined with a user-defined subroutine. From these results, it was demonstrated that the proposed anisotropic viscoelastic composite shell simulation technique can be successfully used to predict warpage of multi-layer PCBs during the reflow process.
NASA Astrophysics Data System (ADS)
Fernandez, N.; Kaus, B. J. P.
2012-04-01
Many fold-and-thrust belts are dominated by crustal scale folding that exhibits fairly regular fold spacing. For example, the Fars region in the Zagros Mountains shows a fold spacing with a normal distribution around a dominant wavelength of 14 Km ± 3 Km, yet having a wide variability of aspect ratios (length to wavelength ratios; Yamato et al., 2011). To which extend this is consistent with a crustal-scale folding instability or how the regional spacing of folding can be used to constrain regional rheological parameters are not fully resolved questions. To get insights into these problems we have investigated the dominant wavelength selection and evolution in a true multilayer system (Schmid and Podlachikov, 2006) with three different viscosities: lower salt layer (ηs), and overlying weak layers (ηw) and competent layers (ηc). This has been done by means of two tools: a semi-analytical solution and numerical models. The 2D semi-analytical approach was applied to derive mechanical phase diagrams that can be used to distinguish different folding modes using two viscosity ratios (R1= ηc/ ηs and R2= ηc/ ηw). To test the validity of the phase diagrams beyond the initial stages of folding for which the analytical approach is valid, we performed several 3D high-resolution forward numerical runs using a finite element code (LaMEM). Additionally, irregular bottom topography was implemented in the numerical runs in order to account for variable salt thickness distribution and consequently study its effect on the wavelength selection. A straight but gradual salt thickness variation, sudden thickness variations due to a basement step or an arc shaped salt basin among other cases could be investigated. It was observed that the bottom topography exerts an impact on the velocity field of the different folding modes and as a result, its influence can be observed on the resulting topography. However, not all the folding modes exhibit an initial wavelength that is dependent
ERIC Educational Resources Information Center
Wulf, Kathleen M.; And Others
1980-01-01
An analysis of the massive amount of literature pertaining to the improvement of professional instruction in dental education resulted in the formation of a comprehensive model of 10 categories, including Delphi technique; systems approach; agencies; workshops; multi-media, self-instruction; evaluation paradigms, measurement, courses, and…
Federal Register 2010, 2011, 2012, 2013, 2014
2013-08-01
... COMMISSION Certain Digital Models, Digital Data, and Treatment Plans for Use in Making Incremental Dental Appliances, the Appliances Made Therefrom, and Methods of Making Same; Notice of Commission Determination To... (``Align''), on March 1, 2012, as corrected on March 22, 2012. 77 FR 20648 (April 5, 2012). The...
Federal Register 2010, 2011, 2012, 2013, 2014
2013-05-17
... From the Federal Register Online via the Government Publishing Office INTERNATIONAL TRADE COMMISSION Certain Digital Models, Digital Data, and Treatment Plans for Use, in Making Incremental Dental Positioning Adjustment Appliances Made Therefrom, and Methods of Making the Same Investigation No. 337-...
Federal Register 2010, 2011, 2012, 2013, 2014
2013-08-01
... COMMISSION Certain Digital Models, Digital Data, and Treatment Plans for Use in Making Incremental Dental Appliances, the Appliances Made Therefrom, and Methods of Making Same; Notice of Commission Determination To... (``Align''), on March 1, 2012, as corrected on March 22, 2012. 77 FR 20648 (April 5, 2012). The...
NASA Astrophysics Data System (ADS)
Matin, M. A.; Oishi, K.; Katsuta, A.; Akai, D.; Sawada, K.; Ishida, M.
2015-07-01
Using combined experimental and simulation techniques, this study addresses the critical stress for peeling off crucial layer(s) in multilayered epitaxial functional thin films on n-Si(001) substrate. The thickness of platinum (Pt) and PZT thin films was varied from 22 nm to 142 nm and 90 nm to 450 nm, respectively. Residual stresses were measured by analyzing captured fringes using Newton's rings technique. Advanced finite element computation was next conducted to predict the evolution of residual stresses. Induced stresses in Pt thin film were found to be decreased with decreasing the thickness of film from 72 nm to 40 nm. In contrast, stresses are shown to be decreased with increasing the thickness of PZT film from 240 nm to 450 nm. The design of the pyroelectric multilayered sensors was thus optimized employing finite element (FE) simulation. Computed stresses were found to correlate well with that observed in experiments. FE simulations can thus be used as a tool to a priori predict the evolution of residual stresses, which may allow a fail-safe design before the fabrication of pyroelectric image sensors.
NASA Astrophysics Data System (ADS)
Andrei, Petru; Mehta, Mohit; Dimian, Mihai
2014-02-01
A generalized Jiles-Atherton model is proposed to describe mixed clockwise and counter-clockwise hysteresis loops. While it is physically inconsistent for homogeneous magnetic materials, this mixed type of hysteresis is exhibited by several multi-layer and superlattice materials with antiferromagnetic coupling. The modeling approach is based on a newly developed clockwise hysteretic model using the Jiles-Atherton framework and its linear superposition to the classical counter-clockwise version. The resulting technique is implemented in open-access academic software for hysteresis and simulation samples are presented in the paper.
NASA Astrophysics Data System (ADS)
Guillemot, C.; Clerot, F.
A new model for long-wavelength longitudinal optical phonons in GaAsGaAlAs multi-layer structures is presented. Depending on the layer, the relative ionic displacements are written on the basis of GaAs or GaAs-type longitudinal optical phonons and treated in the framework of the Born-Huang model generalized to include isotropic dispersion effects in the Brillouin zone centre. For double heterostructures, a finite number of quantized confined modes is found. Interplay between the long range Coulomb interaction, which couples the vibrations of adjacent GaAs layers, and confinement effects, which prevent the displacements of adjacent GaAs layers to overlap, is evidenced in the case of superlattices. The strength of the electron-phonon coupling in double heterostructures stays within a factor of 2 of the electron-bulk phonon effective coupling strength for practical values of the parameters.
Lane, M.; Chaiken, A.; Michel, R.P.
1994-12-01
We have characterized thin-film multilayers grown by ion-beam sputtering using magnetization curves and modeling of low-angle x-ray diffraction data. In our films, we use ferromagnetic layer = Co, Fe, and NiFe and spacer layer = Si, Ge, FeSi{sub 2}, and CoSi{sub 2}. We have studied the effects of (1) deposition conditions; (2) thickness of layers; (3) different layer materials; and (4) annealing. We find higher magnetization in films grown at 1000V rather than 500V and in films with spacer layers of 50{angstrom} rather than 100{angstrom}. We find higher coercivity in films with cobalt grown on germanium rather than silicon, metal grown on gold underlayers rather than on glass substrates, and when using thinner spacer layers. Finally, modeling reveals that films grown with disilicide layers are more thermally stable than films grown with silicon spacer layers.
Wang, Xiaojing; Chen, Ming-Hui; Yan, Jun
2013-07-01
Cox models with time-varying coefficients offer great flexibility in capturing the temporal dynamics of covariate effects on event times, which could be hidden from a Cox proportional hazards model. Methodology development for varying coefficient Cox models, however, has been largely limited to right censored data; only limited work on interval censored data has been done. In most existing methods for varying coefficient models, analysts need to specify which covariate coefficients are time-varying and which are not at the time of fitting. We propose a dynamic Cox regression model for interval censored data in a Bayesian framework, where the coefficient curves are piecewise constant but the number of pieces and the jump points are covariate specific and estimated from the data. The model automatically determines the extent to which the temporal dynamics is needed for each covariate, resulting in smoother and more stable curve estimates. The posterior computation is carried out via an efficient reversible jump Markov chain Monte Carlo algorithm. Inference of each coefficient is based on an average of models with different number of pieces and jump points. A simulation study with three covariates, each with a coefficient of different degree in temporal dynamics, confirmed that the dynamic model is preferred to the existing time-varying model in terms of model comparison criteria through conditional predictive ordinate. When applied to a dental health data of children with age between 7 and 12 years, the dynamic model reveals that the relative risk of emergence of permanent tooth 24 between children with and without an infected primary predecessor is the highest at around age 7.5, and that it gradually reduces to one after age 11. These findings were not seen from the existing studies with Cox proportional hazards models. PMID:23389549
NASA Astrophysics Data System (ADS)
Tabari, Hossein; Hosseinzadeh Talaee, P.; Abghari, Hirad
2012-05-01
Estimation of pan evaporation ( E pan) using black-box models has received a great deal of attention in developing countries where measurements of E pan are spatially and temporally limited. Multilayer perceptron (MLP) and coactive neuro-fuzzy inference system (CANFIS) models were used to predict daily E pan for a semi-arid region of Iran. Six MLP and CANFIS models comprising various combinations of daily meteorological parameters were developed. The performances of the models were tested using correlation coefficient ( r), root mean square error (RMSE), mean absolute error (MAE) and percentage error of estimate (PE). It was found that the MLP6 model with the Momentum learning algorithm and the Tanh activation function, which requires all input parameters, presented the most accurate E pan predictions ( r = 0.97, RMSE = 0.81 mm day-1, MAE = 0.63 mm day-1 and PE = 0.58 %). The results also showed that the most accurate E pan predictions with a CANFIS model can be achieved with the Takagi-Sugeno-Kang (TSK) fuzzy model and the Gaussian membership function. Overall performances revealed that the MLP method was better suited than CANFIS method for modeling the E pan process.
Ultrasonic NDE of Multilayered Structures
Quarry, M J; Fisher, K A; Lehman, S K
2005-02-14
This project developed ultrasonic nondestructive evaluation techniques based on guided and bulk waves in multilayered structures using arrays. First, a guided wave technique was developed by preferentially exciting dominant modes with energy in the layer of interest via an ultrasonic array. Second, a bulk wave technique uses Fermat's principle of least time as well as wave-based properties to reconstruct array data and image the multilayered structure. The guided wave technique enables the inspection of inaccessible areas of a multilayered structure without disassembling it. Guided waves propagate using the multilayer as a waveguide into the inaccessible areas from an accessible position. Inspecting multi-layered structures with a guided wave relies on exciting modes with sufficient energy in the layer of interest. Multilayered structures are modeled to determine the possible modes and their distribution of energy across the thickness. Suitable modes were determined and excited by designing arrays with the proper element spacing and frequency. Bulk wave imaging algorithms were developed to overcome the difficulties of multiple reflections and refractions at interfaces. Reconstruction algorithms were developed to detect and localize flaws. A bent-ray algorithm incorporates Fermat's principle to correct time delays in the ultrasonic data that result from the difference in wave speeds in each layer and refractions at the interfaces. A planar wave-based algorithm was developed using the Green function for the multilayer structure to enhance focusing on reception for improved imaging.
Dental arch changes associated with rapid maxillary expansion: A retrospective model analysis study
D’Souza, Ivor M; Kumar, H. C. Kiran; Shetty, K. Sadashiva
2015-01-01
Introduction: Transverse deficiency of the maxilla is a common clinical problem in orthodontics and dentofacial orthopedics. Transverse maxillary deficiency, isolated or associated with other dentofacial deformities, results in esthetic and functional impairment giving rise to several clinical manifestations such as asymmetrical facial growth, positional and functional mandibular deviations, altered dentofacial esthetics, adverse periodontal responses, unstable dental tipping, and other functional problems. Orthopedic maxillary expansion is the preferred treatment approach to increase the maxillary transverse dimension in young patients by splitting of the mid palatal suture. This orthopedic procedure has lately been subject of renewed interest in orthodontic treatment mechanics because of its potential for increasing arch perimeter to alleviate crowding in the maxillary arch without adversely affecting facial profile. Hence, the present investigation was conducted to establish a correlation between transverse expansion and changes in the arch perimeter, arch width and arch length. Methods: For this purpose, 10 subjects (five males, five females) were selected who had been treated by rapid maxillary expansion (RME) using hyrax rapid palatal expander followed by fixed mechanotherapy (PEA). Pretreatment (T1), postexpansion (T2), and posttreatment (T3) dental models were compared for dental changes brought about by RME treatment and its stability at the end of fixed mechanotherapy. After model measurements were made, the changes between T1–T2, T2–T3 and T1–T3 were determined for each patient. The mean difference between T1–T2, T2–T3 and T1–T3 were compared to assess the effects of RME on dental arch measurements. Results are expressed as mean ± standard deviation and are compared by repeated measures analysis of variance followed by a post-hoc test. Arch perimeter changes are correlated with changes in arch widths at the canine, premolar and molar regions
Valentín, A.; Humphrey, J.D.; Holzapfel, G.A.
2011-01-01
Arterial responses to diverse pathologies and insults likely occur via similar mechanisms. For example, many studies suggest that the natural process of aging and isolated systolic hypertension share many characteristics in arteries, including loss of functional elastin, decreased smooth muscle tone, and altered rates of deposition and/or cross-linking of fibrillar collagen. Our aim is to show computationally how these coupled effects can impact evolving aortic geometry and mechanical behavior. Employing a thick-walled, multi-layered constrained mixture model, we suggest that a coupled loss of elastin and vasoactive function are fundamental mechanisms by which aortic aging occurs. Moreover, it is suggested that collagenous stiffening, although itself generally an undesirable process, can play a key role in attenuating excessive dilatation, perhaps including the enlargement of abdominal aortic aneurysms. PMID:21380570
Damage modeling of small-scale experiments on dental enamel with hierarchical microstructure.
Scheider, I; Xiao, T; Yilmaz, E; Schneider, G A; Huber, N; Bargmann, S
2015-03-01
Dental enamel is a highly anisotropic and heterogeneous material, which exhibits an optimal reliability with respect to the various loads occurring over years. In this work, enamel's microstructure of parallel aligned rods of mineral fibers is modeled and mechanical properties are evaluated in terms of strength and toughness with the help of a multiscale modeling method. The established model is validated by comparing it with the stress-strain curves identified by microcantilever beam experiments extracted from these rods. Moreover, in order to gain further insight in the damage-tolerant behavior of enamel, the size of crystallites below which the structure becomes insensitive to flaws is studied by a microstructural finite element model. The assumption regarding the fiber strength is verified by a numerical study leading to accordance of fiber size and flaw tolerance size, and the debonding strength is estimated by optimizing the failure behavior of the microstructure on the hierarchical level above the individual fibers. Based on these well-grounded properties, the material behavior is predicted well by homogenization of a representative unit cell including damage, taking imperfections (like microcracks in the present case) into account. PMID:25484332
Mathematical modeling of cross-linking monomer elution from resin-based dental composites.
Manojlovic, Dragica; Radisic, Marina; Lausevic, Mila; Zivkovic, Slavoljub; Miletic, Vesna
2013-01-01
Elution of potentially toxic substances, including monomers, from resin-based dental composites may affect the biocompatibility of these materials in clinical conditions. In addition to the amounts of eluted monomers, mathematical modeling of elution kinetics reveals composite restorations as potential chronic sources of leachable monomers. The aim of this work was to experimentally quantify elution of main cross-linking monomers from four commercial composites and offer a mathematical model of elution kinetics. Composite samples (n = 7 per group) of Filtek Supreme XT (3M ESPE), Tetric EvoCeram (Ivoclar Vivadent), Admira (Voco), and Filtek Z250 (3M ESPE) were prepared in 2-mm thick Teflon moulds and cured with halogen or light-emitting diode light. Monomer elution in ethanol and water was analyzed using high-performance liquid chromatography up to 28 days postimmersion. The mathematical model was expressed as a sum of two exponential regression functions representing the first-order kinetics law. Elution kinetics in all cases followed the same mathematical model though differences in rate constants as well as the extent of monomer elution were material-, LCU-, medium-dependent. The proposed mechanisms of elution indicate fast elution from surface and subsurface layers and up to 100 times slower monomer extraction from the bulk polymer. PMID:22997145
Antimicrobial polypeptide multilayer nanocoatings.
Rudra, Jai S; Dave, Komal; Haynie, Donald T
2006-01-01
A multilayer coating (or film) of nanometer-thick layers can be made by sequential adsorption of oppositely charged polyelectrolytes on a solid support. The method is known as layer-by-layer assembly (LBL). No special apparatus is required for LBL and nanofilms can be prepared under mild, physiological conditions. A multilayer nanofilm in which at least one of the constituent species is a polypeptide is a polypeptide multilayer nanofilm. The present work was aimed at assessing whether polypeptide multilayer nanofilms with specific antimicrobial properties could be prepared by incorporation of a known antimicrobial agent in the film structure, in this case the edible protein hen egg white lysozyme (HEWL). The chicken enzyme is widely employed as a human food preservative. An advantage of LBL in this context is that the nanofilm is fabricated directly on the surface of interest, eliminating the need to incorporate the antimicrobial in other packaging materials. Here, nanofilms were made of poly(L-glutamic acid) (PLGA), which is highly negatively charged in the mildly acidic pH range, and HEWL, which has a high net positive charge at acidic pH. We show that PLGA/HEWL nanofilms inhibit growth of the model microbe Microccocus luteus in the surrounding liquid medium. The amount of HEWL released from PLGA/HEWL films depends on the number of HEWL layers and therefore on the total quantity of HEWL in the films. This initial study provides a sketch of the scope for further development of LBL in the area of antimicrobial polypeptide multilayer films. Potential applications of such films include strategies for food preservation and coatings for implant devices. PMID:17176751
... anatomy, patient management, and periodontics, which is the study of gum disease. High school students interested in becoming dental hygienists should take courses in biology, chemistry, and math. Most dental hygiene programs also require applicants to have completed at ...
... this page: //medlineplus.gov/ency/patientinstructions/000779.htm Dental sealants To use the sharing features on this ... case a sealant needs to be replaced. How Dental Sealants Are Applied Your dentist applies sealants on ...
Liang, D.; Xu, X.; Tsang, L.; Andreadis, K.M.; Josberger, E.G.
2008-01-01
The Dense Media Radiative Transfer theory (DMRT) of Quasicrystalline Approximation of Mie scattering by sticky particles is used to study the multiple scattering effects in layered snow in microwave remote sensing. Results are illustrated for various snow profile characteristics. Polarization differences and frequency dependences of multilayer snow model are significantly different from that of the single-layer snow model. Comparisons are also made with CLPX data using snow parameters as given by the VIC model. ?? 2007 IEEE.
A new multilayered visco-elasto-plastic experimental model to study strike-slip fault seismic cycle
NASA Astrophysics Data System (ADS)
Caniven, Y.; Dominguez, S.; Soliva, R.; Cattin, R.; Peyret, M.; Marchandon, M.; Romano, C.; Strak, V.
2015-02-01
Nowadays, technological advances in satellite imagery measurements as well as the development of dense geodetic and seismologic networks allow for a detailed analysis of surface deformation associated with active fault seismic cycle. However, the study of earthquake dynamics faces several limiting factors related to the difficulty to access the deep source of earthquake and to integrate the characteristic time scales of deformation processes that extend from seconds to thousands of years. To overcome part of these limitations and better constrain the role and couplings between kinematic and mechanical parameters, we have developed a new experimental approach allowing for the simulation of strike-slip fault earthquakes and analyze in detail hundreds of successive seismic cycle. Model rheology is made of multilayered visco-elasto-plastic analog materials to account for the mechanical behavior of the upper and lower crust and to allow simulating brittle/ductile coupling, postseismic deformation phase and far-field stress transfers. The kinematic evolution of the model surface is monitored using an optical system, based on subpixel spectral correlation of high-resolution digital images. First, results show that the model succeed in reproducing the deformation mechanisms and surface kinematics associated to the main phases of the seismic cycle indicating that model scaling is satisfactory. These results are comforted by using numerical algorithms to study the strain and stress distribution at the surface and at depth, along the fault plane. Our analog modeling approach appears, then, as an efficient complementary approach to investigate earthquake dynamics.
Ghirardello, Davide; Morselli, Melissa; Semplice, Matteo; Di Guardo, Antonio
2010-12-01
A new site-specific, dynamic model (SoilPlus) was developed to simulate the fate of nonionized organic chemicals in the air/litter/soil system; key features of the model are the double-layered air compartment interacting dynamically with multilayered litter and soil compartments, with seasonal dissolved organic carbon (DOC) fluxes. The model describes the soil environment calculating separate mass balances for water, chemical, and organic matter. SoilPlus underwent a process of benchmarking and evaluation in order to reach a satisfying confirmation of its predictive capability. Several simulations were performed to estimate the role of litter and DOC in affecting the fate of a model contaminant for POPs (hexachlorobenzene). The model shows that litter can behave as a buffer in the process of transferring hexachlorobenzene from air to the mineral soil and as a trap when hexachlorobenzene tends to move from a contaminated field toward clean air. DOC seems to behave as a leaching-enhancer in certain climatic conditions (heavy rainfall, high DOC concentrations), but it does not appear to move significant amounts of HCB in a year calculation. PMID:21053937
NASA Astrophysics Data System (ADS)
Chan, Henry; Masserey, Bernard; Fromme, Paul
2015-02-01
Especially for ageing aircraft the development of fatigue cracks at fastener holes due to stress concentration and varying loading conditions constitutes a significant maintenance problem. High frequency guided waves offer a potential compromise between the capabilities of local bulk ultrasonic measurements with proven defect detection sensitivity and the large area coverage of lower frequency guided ultrasonic waves. High frequency guided waves have energy distributed through all layers of the specimen thickness, allowing in principle hidden (2nd layer) fatigue damage monitoring. For the integration into structural health monitoring systems the sensitivity for the detection of hidden fatigue damage in inaccessible locations of the multi-layered components from a stand-off distance has to be ascertained. The multi-layered model structure investigated consists of two aluminium plate-strips with an epoxy sealant layer. During cyclic loading fatigue crack growth at a fastener hole was monitored. Specific guided wave modes (combination of fundamental A0 and S0 Lamb modes) were selectively excited above the cut-off frequencies of higher modes using a standard ultrasonic wedge transducer. Non-contact laser measurements close to the defect were performed to qualify the influence of a fatigue crack in one aluminium layer on the guided wave scattering. Fatigue crack growth monitoring using laser interferometry showed good sensitivity and repeatability for the reliable detection of small, quarter-elliptical cracks. Standard ultrasonic pulse-echo equipment was employed to monitor hidden fatigue damage from a stand-off distance without access to the damaged specimen layer. Sufficient sensitivity for the detection of fatigue cracks located in the inaccessible aluminium layer was verified, allowing in principle practical in situ ultrasonic monitoring of fatigue crack growth.
Hydroxyapatite induces spontaneous polymerization of model self-etch dental adhesives.
Zhang, Ying; Wu, Ningjing; Bai, Xinyan; Xu, Changqi; Liu, Yi; Wang, Yong
2013-10-01
The objective of this study is to report for the first time the spontaneous polymerization phenomenon of self-etch dental adhesives induced by hydroxylapatite (HAp). Model self-etch adhesives were prepared by using a monomer mixture of bis[2-(methacryloyloxy)ethyl] phosphate (2MP) with 2-hydroxyethyl methacrylate (HEMA). The initiator system consisted of camphorquinone (CQ, 0.022 mmol/g) and ethyl 4-dimethylaminobenzoate (4E, 0.022-0.088 mmol/g). HAp (2-8 wt.%) was added to the neat model adhesive. In a dark environment, the polymerization was monitored in-situ using ATR/FT-IR, and the mechanical properties of the polymerized adhesives were evaluated using nanoindentation technique. Results indicated that spontaneous polymerization was not observed in the absence of HAp. However, as different amounts of HAp were incorporated into the adhesives, spontaneous polymerization was induced. Higher HAp content led to higher degree of conversion (DC), higher rate of polymerization (RP) and shorter induction period (IP). In addition, higher 4E content also elevated DC and RP and reduced IP of the adhesives. Nanoindentation result suggested that the Young's modulus of the polymerized adhesives showed similar dependence on HAp and 4E contents. In summary, interaction with HAp could induce spontaneous polymerization of the model self-etch adhesives. This result provides important information for understanding the initiation mechanism of the self-etch adhesives, and may be of clinical significance to strengthen the adhesive/dentin interface based on the finding. PMID:23910263
Finite element modeling of dental restoration through multi-material laser densification
NASA Astrophysics Data System (ADS)
Dai, Kun
To provide guidance for intelligent selection of various parameters in the Multi-Material Laser Densification (MMLD) process for dental restorations, finite element modeling (FEM) has been carried out to investigate the MMLD process. These modeling investigations include the thermal analysis of the nominal surface temperature that should be adopted during experiments in order to achieve the desired microstructure; the effects of the volume shrinkage due to transformation from a powder compact to dense liquid on the temperature distribution and the size of the transformation zone; the evolution of transient temperature, transient stresses, residual stresses and distortions; and the effects of laser processing conditions, such as fabrication sequences, laser scanning patterns, component sizes, preheating temperatures, laser scanning rates, initial porosities, and thicknesses of each powder layer, on the final quality of the component fabricated via the MMLD process. The simulation results are compared with the experiments. It is found that the predicted temperature distribution matches the experiments very well. The nominal surface temperature applied on the dental porcelain body should be below 1273 K to prevent the forming of the un-desired microstructure (i.e., a leucite-free glassy phase). The simplified models that do not include the volume shrinkage effect provide good estimations of the temperature field and the size of the laser-densified body, although the shape of the laser-densified body predicted is different from that obtained in the experiment. It is also fount that warping and residual thermal stresses of the laser-densified component are more sensitive to the chamber preheating temperature and the thickness of each powder layer than to the laser scanning rate and the initial porosity of the powder layer. The major mechanism responsible for these phenomena is identified to be related to the change of the temperature gradient induced by these laser
Modeling of the Light Speckle Field Structure Inside a Multilayer Human Skin Tissue
NASA Astrophysics Data System (ADS)
Barun, V. V.; Dik, S. K.; Ivanov, A. P.; Abramovich, N. D.
2013-11-01
We present an analytic method and the results of investigating the characteristics of the interference pattern formed by multiply scattered light in a multilayer biological tissue of the type of human skin at the wavelengths of the visible and neat IR spectral regions under laser irradiation. Calculations were performed with the use of the known solutions of the equations of radiation transfer in the biotissue and the relation between the theory of propagation of light in a scattering medium and the coherence theory. The radial structure of the light field in the depth of the human skin formed by coherent and incoherent radiation depending on its biophysical parameters has been investigated. The characteristic sizes of speckles in each layer of the skin have been estimated. The biophysical factors connected with the volume concentration of blood in the dermis and the degree of its oxygenation influencing the contrast of the speckle pattern in the dermis have been discussed. The possibility of formulating and solving inverse problems of biomedical optics on the restoration of blood parameters from measurements of speckle characteristics has been shown.
Rutqvist, Jonny; Birkholzer, Jens; Tsang, Chin-Fu
2006-01-01
This paper presents a numerical study of coupled hydrological and geomechanical processes during a deep underground injection of supercritical CO{sub 2} in a hypothetical brine aquifer. We consider a multilayer system in which the injection zone is situated below a sequence of caprock and aquifer layers that are intersected by a vertical fault zone. The fault zone consists of highly fractured shale across the first caprock layers that are located just above the injection zone. Initially, the fractured shale zones are considered sealed with minerals, but we allow fractures (and the fractured zones) to open as a result of injection induced reductions in effective stresses. Our results indicate that even when assuming a very sensitive relationship between effective stress and fractured-zone permeability, the injection-induced changes in permeability across are only moderate with largest changes occurring in the first caprock layer, just above the injection zone. As a result, the upward leakage rate remains relatively small and therefore changes in fluid pressure and hydromechanical effects in overlying zones are also relatively small for the case studied in this paper.
NASA Astrophysics Data System (ADS)
Loredo, A.; Castel, A.
2013-01-01
In this paper, a suitable model for static and dynamic analysis of inhomogeneous anisotropic multilayered plates is described. This model takes into account the variations of the transverse shear strains through the thickness of the plate by means of warping functions. Warping functions are determined by enforcing kinematic and static assumptions at the interfaces. This model leads to: a 10×10 stiffness matrix coupling to each other the membrane strains, the bending and torsion curvatures, and the x and y-derivatives of the transverse shear strains; and a classical 2×2 transverse shear stiffness matrix. This model has been proven to be very efficient, especially when high ratios between the stiffnesses of layers - up to 106 - are present. This work is related to Woodcock's model, so it can be seen as a reformulation of his work. However, it brings several enhancements: the displacement field is made explicit; it is reformulated with commonly used plate notations; laminate equations of motion are fully detailed; the place of this model among other plate models is now easy to see and is discussed; the link between this formulation and the original one is completely written with all necessary proofs; misses and errors have been found in the energy coefficients of the original work and have been corrected; it is now easy to improve or to adapt the model for specific applications with the choice of refined or specific warping functions. Static deflection and natural frequencies for isotropic and anisotropic sandwich plates are given and compared to other models: they show that the present model is very accurate for the simulation of such structures.
NASA Astrophysics Data System (ADS)
Ibey, Bennett L.; Lee, Seungjoon; Ericson, M. Nance; Wilson, Mark A.; Cote, Gerard L.
2004-06-01
A Multi-Layer Monte Carlo (MLMC) model was developed to predict the results of in vivo blood perfusion and oxygenation measurement of transplanted organs as measured by an indwelling optical sensor. A sensor has been developed which uses three-source excitation in the red and infrared ranges (660, 810, 940 nm). In vitro data was taken using this sensor by changing the oxygenation state of whole blood and passing it through a single-tube pump system wrapped in bovine liver tissue. The collected data showed that the red signal increased as blood oxygenation increased and infrared signal decreased. The center wavelength of 810 nanometers was shown to be quite indifferent to blood oxygenation change. A model was developed using MLMC code that sampled the wavelength range from 600-1000 nanometers every 6 nanometers. Using scattering and absorption data for blood and liver tissue within this wavelength range, a five-layer model was developed (tissue, clear tubing, blood, clear tubing, tissue). The theoretical data generated from this model was compared to the in vitro data and showed good correlation with changing blood oxygenation.
Taravat, Alireza; Oppelt, Natascha
2014-01-01
Oil spills represent a major threat to ocean ecosystems and their environmental status. Previous studies have shown that Synthetic Aperture Radar (SAR), as its recording is independent of clouds and weather, can be effectively used for the detection and classification of oil spills. Dark formation detection is the first and critical stage in oil-spill detection procedures. In this paper, a novel approach for automated dark-spot detection in SAR imagery is presented. A new approach from the combination of adaptive Weibull Multiplicative Model (WMM) and MultiLayer Perceptron (MLP) neural networks is proposed to differentiate between dark spots and the background. The results have been compared with the results of a model combining non-adaptive WMM and pulse coupled neural networks. The presented approach overcomes the non-adaptive WMM filter setting parameters by developing an adaptive WMM model which is a step ahead towards a full automatic dark spot detection. The proposed approach was tested on 60 ENVISAT and ERS2 images which contained dark spots. For the overall dataset, an average accuracy of 94.65% was obtained. Our experimental results demonstrate that the proposed approach is very robust and effective where the non-adaptive WMM & pulse coupled neural network (PCNN) model generates poor accuracies. PMID:25474376
3D-VAR multilayer assimilation of X-band SAR data into a detailed snowpack model
NASA Astrophysics Data System (ADS)
Phan, X. V.; Ferro-Famil, L.; Gay, M.; Durand, Y.; Dumont, M.; Morin, S.; Allain, S.; D'Urso, G.; Girard, A.
2013-10-01
We introduce a variational data assimilation scheme to assimilate X-band Synthetic Aperture Radar (SAR) data into a snowpack evolution model. The structure properties of a snowpack, such as snow density and grain optical diameter of each layer, are simulated over a period of time by the snow metamorphism model Crocus, fed by the local reanalysis SAFRAN at a French alpine location. These parameters are used as inputs of an Electromagnetic Backscattering Model (EBM) based on Dense Media Radiative Transfer (DMRT) theory, which calculates the simulated total backscattering coefficient. Next, 3D-VAR data assimilation is implemented in order to minimize the discrepancies between model simulations and observations obtained from SAR acquisitions, by modifying the parameters of a multilayer snowpack calculated by Crocus. The algorithm then reinitializes Crocus with the optimized snowpack structure properties, and therefore allows it to continue the simulation of snowpack evolution where adjustments based on remote sensing data has been taken into account. Results obtained using TerraSAR-X acquisitions on Argentière Glacier (Mont-Blanc massif, French Alps) show the high potential of this method for improving snow cover simulation.
Taravat, Alireza; Oppelt, Natascha
2014-01-01
Oil spills represent a major threat to ocean ecosystems and their environmental status. Previous studies have shown that Synthetic Aperture Radar (SAR), as its recording is independent of clouds and weather, can be effectively used for the detection and classification of oil spills. Dark formation detection is the first and critical stage in oil-spill detection procedures. In this paper, a novel approach for automated dark-spot detection in SAR imagery is presented. A new approach from the combination of adaptive Weibull Multiplicative Model (WMM) and MultiLayer Perceptron (MLP) neural networks is proposed to differentiate between dark spots and the background. The results have been compared with the results of a model combining non-adaptive WMM and pulse coupled neural networks. The presented approach overcomes the non-adaptive WMM filter setting parameters by developing an adaptive WMM model which is a step ahead towards a full automatic dark spot detection. The proposed approach was tested on 60 ENVISAT and ERS2 images which contained dark spots. For the overall dataset, an average accuracy of 94.65% was obtained. Our experimental results demonstrate that the proposed approach is very robust and effective where the non-adaptive WMM & pulse coupled neural network (PCNN) model generates poor accuracies. PMID:25474376
NASA Astrophysics Data System (ADS)
Colston, Bill W.; Sathyam, Ujwal S.; Dasilva, Luiz B.; Everett, Matthew J.; Stroeve, Pieter; Otis, L. L.
1998-09-01
We present here the first in vivo optical coherence tomography (OCT) images of human dental tissue. A novel dental optical coherence tomography system has been developed. This system incorporates the interferometer sample arm and transverse scanning optics into a handpiece that can be used intraorally to image human dental tissues. The average imaging depth of this system varied from 3 mm in hard tissues to 1.5 mm in soft tissues. We discuss the application of this imaging system for dentistry and illustrate the potential of our dental OCT system for diagnosis of periodontal disease, detection of caries, and evaluation of dental restorations.
Craniofacial and Dental Defects in the Col1a1Jrt/+ Mouse Model of Osteogenesis Imperfecta.
Eimar, H; Tamimi, F; Retrouvey, J-M; Rauch, F; Aubin, J E; McKee, M D
2016-07-01
Certain mutations in the COL1A1 and COL1A2 genes produce clinical symptoms of both osteogenesis imperfecta (OI) and Ehlers-Danlos syndrome (EDS) that include abnormal craniofacial growth, dental malocclusion, and dentinogenesis imperfecta. A mouse model (Col1a1(Jrt)/+) was recently developed that had a skeletal phenotype and other features consistent with moderate-to-severe OI and also with EDS. The craniofacial phenotype of 4- and 20-wk-old Col1a1(Jrt)/+ mice and wild-type littermates was assessed by micro-computed tomography (µCT) and morphometry. Teeth and the periodontal ligament compartment were analyzed by µCT, light microscopy/histomorphometry, and electron microscopy. Over time, at 20 wk, Col1a1(Jrt)/+ mice developed smaller heads, a shortened anterior cranial base, class III occlusion, and a mandibular side shift with shorter morphology in the masticatory region (maxilla and mandible). Col1a1(Jrt)/+ mice also had changes in the periodontal compartment and abnormalities in the dentin matrix and mineralization. These findings validate Col1a1(Jrt)/+ mice as a model for OI and EDS in humans. PMID:26951553
Detecting reduced bone mineral density from dental radiographs using statistical shape models.
Allen, P Danny; Graham, Jim; Farnell, Damian J J; Harrison, Elizabeth J; Jacobs, Reinhilde; Nicopolou-Karayianni, Kety; Lindh, Christina; van der Stelt, Paul F; Horner, Keith; Devlin, Hugh
2007-11-01
We describe a novel method of estimating reduced bone mineral density (BMD) from dental panoramic tomograms (DPTs), which show the entire mandible. Careful expert width measurement of the inferior mandibular cortex has been shown to be predictive of BMD in hip and spine osteopenia and osteoporosis. We have implemented a method of automatic measurement of the width by active shape model search, using as training data 132 DPTs of female subjects whose BMD has been established by dual-energy X-ray absorptiometry. We demonstrate that widths measured after fully automatic search are significantly correlated with BMD, and exhibit less variability than manual measurements made by different experts. The correlation is highest towards the lateral region of the mandible, in a position different from that previously employed for manual width measurement. An receiver-operator characterstic (ROC) analysis for identifying osteopenia (T < -1: BMD more than one standard deviation below that of young healthy females) gives an area under curve (AUC) value of 0.64. Using a minimal interaction to initiate active shape model (ASM) search, the measurement can be made at the optimum region of the mandible, resulting in an AUC value of 0.71. Using an independent test set, AUC for detection of osteoporosis (T < -2.5) is 0.81. PMID:18046935
Influence of peak power in ablation rate of dental hard tissues: mathematical model
NASA Astrophysics Data System (ADS)
Colojoara, Carmen; Gabay, Shimon; van der Meulen, Freerk W.; van Gemert, Martin J. C.
1996-12-01
Pulsed Er:YAG and CO2 lasers should be suitable instruments for dentin and enamel ablation because both tissues have absorption peaks for radiation at 2.9 and 9.6 micrometers wavelengths. This is the context of our research that emphasizes the way in which the diameter and the depth of the crater made in enamel and dentin with the laser Er:YAG and CO2 is influenced in quantity and quality. Freshly extracted human third molar were used for this experiment. The laser source is Er:YAG Kavo Key dental model 1240 and CO2 Laser Sonics LS 860. The dimensions of the obtained craters were measured using the optical microscopy method. The obtained results were modelled experimentally with programs: GRAPHER and STATGRAPHICS. After the mathematical processing to the results what we obtain is relevant regarding the influence of the key parameters in the efficiency of the ablation according to the type of laser. On the whole, from our research results that both lasers ablate efficiently the dentin when the laser energy is between 200 and 300 mJ.
Herget, Philipp; O'Sullivan, Eugene J.; Romankiw, Lubomyr T.; Wang, Naigang; Webb, Bucknell C.
2016-07-05
A mechanism is provided for an integrated laminated magnetic device. A substrate and a multilayer stack structure form the device. The multilayer stack structure includes alternating magnetic layers and diode structures formed on the substrate. Each magnetic layer in the multilayer stack structure is separated from another magnetic layer in the multilayer stack structure by a diode structure.
Mohd Yusof, Mohd Yusmiaidil Putera; Cauwels, Rita; Deschepper, Ellen; Martens, Luc
2015-08-01
The third molar development (TMD) has been widely utilized as one of the radiographic method for dental age estimation. By using the same radiograph of the same individual, third molar eruption (TME) information can be incorporated to the TMD regression model. This study aims to evaluate the performance of dental age estimation in individual method models and the combined model (TMD and TME) based on the classic regressions of multiple linear and principal component analysis. A sample of 705 digital panoramic radiographs of Malay sub-adults aged between 14.1 and 23.8 years was collected. The techniques described by Gleiser and Hunt (modified by Kohler) and Olze were employed to stage the TMD and TME, respectively. The data was divided to develop three respective models based on the two regressions of multiple linear and principal component analysis. The trained models were then validated on the test sample and the accuracy of age prediction was compared between each model. The coefficient of determination (R²) and root mean square error (RMSE) were calculated. In both genders, adjusted R² yielded an increment in the linear regressions of combined model as compared to the individual models. The overall decrease in RMSE was detected in combined model as compared to TMD (0.03-0.06) and TME (0.2-0.8). In principal component regression, low value of adjusted R(2) and high RMSE except in male were exhibited in combined model. Dental age estimation is better predicted using combined model in multiple linear regression models. PMID:26165657
NASA Astrophysics Data System (ADS)
Mesta, M.; van Eersel, H.; Coehoorn, R.; Bobbert, P. A.
2016-03-01
Triplet-triplet annihilation (TTA) and triplet-polaron quenching (TPQ) in organic light-emitting devices (OLEDs) lead to a roll-off of the internal quantum efficiency (IQE) with increasing current density J. We employ a kinetic Monte Carlo modeling study to analyze the measured IQE and color balance as a function of J in a multilayer hybrid white OLED that combines fluorescent blue with phosphorescent green and red emission. We investigate two models for TTA and TPQ involving the phosphorescent green and red emitters: short-range nearest-neighbor quenching and long-range Förster-type quenching. Short-range quenching predicts roll-off to occur at much higher J than measured. Taking long-range quenching with Förster radii for TTA and TPQ equal to twice the Förster radii for exciton transfer leads to a fair description of the measured IQE-J curve, with the major contribution to the roll-off coming from TPQ. The measured decrease of the ratio of phosphorescent to fluorescent component of the emitted light with increasing J is correctly predicted. A proper description of the J-dependence of the ratio of red and green phosphorescent emission needs further model refinements.
Wysen, Kirsten H; Hennessy, Patricia M; Lieberman, Martin I; Garland, Tracy E; Johnson, Susan M
2004-05-01
Kids Get Care is a public health-based program in the Seattle area designed to ensure that low-income children, regardless of insurance status, receive early integrated preventive medical, dental, and developmental health services through attachment to medical and dental homes (the usual sources of medical or dental care). The oral health component of the program focuses on cross-training medical and dental providers, providing partner medical clinics with a case manager, and educating staff in nearby community-based organizations about how to identify incipient dental disease and possible early childhood developmental delays. The program identifies a local, well-respected dentist to champion the delivery of oral health screening within a medical clinic and to provide oral health training to medical clinic staff. The program works with community agencies to educate families on the importance of healthy baby teeth, routine dental care beginning at age one, and general prevention. In its first year, the program trained 355 community staff and 184 primary care providers on how to conduct an oral health assessment. These staff and providers screened more than 5,500 children for oral health problems. One medical clinic more than doubled the number of fluoride varnishes it provided, increasing from 80 to 167 during a nine-month pilot phase. Other outcome studies are in progress. PMID:15186069
Björnsson, Marcus A; Simonsson, Ulrika S H
2011-01-01
AIMS To describe pain intensity (PI) measured on a visual analogue scale (VAS) and dropout due to request for rescue medication after administration of naproxcinod, naproxen or placebo in 242 patients after wisdom tooth removal. METHODS Non-linear mixed effects modelling was used to describe the plasma concentrations of naproxen, either formed from naproxcinod or from naproxen itself, and their relationship to PI and dropout. Goodness of fit was assessed by simultaneous simulations of PI and dropout. RESULTS Baseline PI for the typical patient was 52.7 mm. The PI was influenced by placebo effects, using an exponential model, and by naproxen concentrations using a sigmoid Emax model. Typical maximal placebo effect was a decrease in PI by 20.2%, with an onset rate constant of 0.237 h−1. EC50 was 0.135 µmol l−1. A Weibull time-to-event model was used for the dropout, where the hazard was dependent on the predicted PI and by the PI at baseline. Since the dropout was not at random, it was necessary to include the simulated dropout in visual predictive checks (VPC) of PI. CONCLUSIONS This model describes the relationship between drug effects, PI and the likelihood of dropout after naproxcinod, naproxen and placebo administration. The model provides an opportunity to describe the effects of other doses or formulations, after dental extraction. VPC created by simultaneous simulations of PI and dropout provides a good way of assessing the goodness of fit when there is informative dropout. PMID:21272053
Yoshida, Kenichiro; Nishidate, Izumi
2014-01-01
To rapidly derive a result for diffuse reflectance from a multilayered model that is equivalent to that of a Monte-Carlo simulation (MCS), we propose a combination of a layered white MCS and the adding-doubling method. For slabs with various scattering coefficients assuming a certain anisotropy factor and without absorption, we calculate the transition matrices for light flow with respect to the incident and exit angles. From this series of precalculated transition matrices, we can calculate the transition matrices for the multilayered model with the specific anisotropy factor. The relative errors of the results of this method compared to a conventional MCS were less than 1%. We successfully used this method to estimate the chromophore concentration from the reflectance spectrum of a numerical model of skin and in vivo human skin tissue. PMID:25426319
Modeling the Optical Response to a Near-Field Probe Tip from a Generalized Multilayer Thin Film
NASA Astrophysics Data System (ADS)
Lawrence, A. J.
The contrast mechanism in Kerr imaging is the apparent angle through which the plane of polarization is rotated upon reflection from a magnetic surface. This can be calculated for a well characterized surface given the polarization state of the incident light. As in traditional optical microscopy, the spatial resolution is limited by diffraction to roughly half the wavelength of the illumination light. The diffraction limit can be circumvented through the use of near-field scanning optical microscopy, in which the illumination source is an evanescent field at the tip of a tapered optical fiber. A novel probe design for near-field optical imaging in reflection mode will be proposed, and experimental work on the development of a near-field Kerr microscope performed up to this point will be presented. The complication in merging these two techniques arises from the complex polarization profile of the evanescent field. This profile can be characterized for a given probe geometry with the use of electromagnetic field modeling software, allowing for subsequent modeling of the polarization profile of the optical response. An algorithm for predicting the optical response to a near-field probe tip from a generalized multilayer thin-film is presented.
NASA Astrophysics Data System (ADS)
Vila Verde, A.; Ramos, M. M. D.; Stoneham, A. M.
2007-05-01
Human dental enamel has a porous mesostructure at the nanometre to micrometre scales that affects its thermal and mechanical properties relevant to laser treatment. We exploit finite-element models to investigate the response of this mesostructured enamel to mid-infrared lasers (CO2 at 10.6 µm and Er:YAG at 2.94 µm). Our models might easily be adapted to investigate ablation of other brittle composite materials. The studies clarify the role of pore water in ablation, and lead to an understanding of the different responses of enamel to CO2 and Er:YAG lasers, even though enamel has very similar average properties at the two wavelengths. We are able to suggest effective operating parameters for dental laser ablation, which should aid the introduction of minimally-invasive laser dentistry. In particular, our results indicate that, if pulses of ap10 µs are used, the CO2 laser can ablate dental enamel without melting, and with minimal damage to the pulp of the tooth. Our results also suggest that pulses with 0.1-1 µs duration can induce high stress transients which may cause unwanted cracking.
Time series modeling with pruned multi-layer perceptron and 2-stage damped least-squares method
NASA Astrophysics Data System (ADS)
Voyant, Cyril; Tamas, Wani; Paoli, Christophe; Balu, Aurélia; Muselli, Marc; Nivet, Marie-Laure; Notton, Gilles
2014-03-01
A Multi-Layer Perceptron (MLP) defines a family of artificial neural networks often used in TS modeling and forecasting. Because of its "black box" aspect, many researchers refuse to use it. Moreover, the optimization (often based on the exhaustive approach where "all" configurations are tested) and learning phases of this artificial intelligence tool (often based on the Levenberg-Marquardt algorithm; LMA) are weaknesses of this approach (exhaustively and local minima). These two tasks must be repeated depending on the knowledge of each new problem studied, making the process, long, laborious and not systematically robust. In this paper a pruning process is proposed. This method allows, during the training phase, to carry out an inputs selecting method activating (or not) inter-nodes connections in order to verify if forecasting is improved. We propose to use iteratively the popular damped least-squares method to activate inputs and neurons. A first pass is applied to 10% of the learning sample to determine weights significantly different from 0 and delete other. Then a classical batch process based on LMA is used with the new MLP. The validation is done using 25 measured meteorological TS and cross-comparing the prediction results of the classical LMA and the 2-stage LMA.
Wei, Jingsong; Yan, Hui
2014-11-15
This work focuses on the strong nonlinear saturation absorption (NSA)-induced optical super-resolution effect. A multi-layer system model is proposed to understand the strong NSA-induced formation of an optical pinhole channel and the generation of a super-resolution spot. Taking a Sb2Te3 thin film as an example, numerical simulations were conducted. The results illustrate that an optical pinhole channel is clearly formed by the NSA characteristics. This pinhole channel is similar to a near-field light probe. Light travels through the pinhole channel, and a super-resolution spot is generated at its apex. The near-field spot scanning experimental results show that the reduction ratio of the spot is approximately 44.8%, which is basically consistent with the numerical simulation result of 43%. This work is helpful for understanding optical nonlinear super-resolution effects and developing nanolithography, nanodata storage, high-resolution optical imaging technologies with nonlinear thin films. PMID:25490475
Miura, Seiji; Suzuki, Hidenori; Bae, You Han
2014-01-01
Limited drug distribution is partially responsible for the efficacy gap between preclinical and clinical studies of nano-sized drug carriers for cancer therapy. In this study, we examined the transport behavior of cationic micelles formed from a triblock copolymer of poly(D,L-lactide-co-glycolide)-block-branched polyethyleneimine-block-poly(D,L-lactide-co-glycolide) using a unique in vitro tumor model composed of a multilayered cell culture (MCC) and an Ussing chamber system. The Cy3-labeled cationic micelles showed remarkable Cy3 distribution in the MCC whereas charge-shielded micelles with a poly(ethylene glycol) surface accumulated on the surface of the MCC. Penetration occurred against convectional flow caused by a hydraulic pressure gradient. The study using fluorescence resonance energy transfer (FRET) showed that the cationic micelles dissociate at the interface between the culture media and the MCC or possibly inside of the first-layer cells and penetrates into the MCC as unimers. The penetration and distribution were energy-dependent and suppressed by various endocytic inhibitors. These suggest that cationic unimers mainly utilized clathrin-mediated endocytosis and macropinocytosis for cellular entry and a significant fraction were exocytosed by an unknown mechanism. PMID:25866552